diff --git a/brainpy/dnn/conv.py b/brainpy/dnn/conv.py
index dc39b597..af4ae41d 100644
--- a/brainpy/dnn/conv.py
+++ b/brainpy/dnn/conv.py
@@ -179,7 +179,7 @@ def update(self, x):
         if self.mask is not None:
             try:
                 lax.broadcast_shapes(self.w.shape, self.mask.shape)
-            except:
+            except (ValueError, TypeError):
                 raise ValueError(f"Mask needs to have the same shape as weights. {self.mask.shape} != {self.w.shape}")
             w = w * self.mask
         y = lax.conv_general_dilated(lhs=bm.as_jax(x),
@@ -566,7 +566,7 @@ def update(self, x):
         if self.mask is not None:
             try:
                 lax.broadcast_shapes(self.w.shape, self.mask.shape)
-            except:
+            except (ValueError, TypeError):
                 raise ValueError(f"Mask needs to have the same shape as weights. {self.mask.shape} != {self.w.shape}")
             w = w * self.mask
         y = lax.conv_transpose(lhs=bm.as_jax(x),
diff --git a/brainpy/dnn/interoperation_flax.py b/brainpy/dnn/interoperation_flax.py
index 0b6a1324..6c50a5e1 100644
--- a/brainpy/dnn/interoperation_flax.py
+++ b/brainpy/dnn/interoperation_flax.py
@@ -26,7 +26,7 @@
 try:
     import flax  # noqa
     from flax.linen.recurrent import RNNCellBase
-except:
+except (ImportError, ModuleNotFoundError):
     flax = None
     RNNCellBase = object
 
diff --git a/brainpy/dyn/neurons/lif.py b/brainpy/dyn/neurons/lif.py
index f7ddf886..28d693c3 100644
--- a/brainpy/dyn/neurons/lif.py
+++ b/brainpy/dyn/neurons/lif.py
@@ -299,7 +299,7 @@ def update(self, x=None):
             elif self.spk_reset == 'hard':
                 V += (self.V_reset - V) * spike
             else:
-                raise ValueError
+                raise ValueError(f"Unknown spk_reset mode: {self.spk_reset}. Must be 'soft' or 'hard'.")
 
         else:
             spike = V >= self.V_th
@@ -509,7 +509,7 @@ def update(self, x=None):
             elif self.spk_reset == 'hard':
                 V += (self.V_reset - V) * spike_no_grad
             else:
-                raise ValueError
+                raise ValueError(f"Unknown spk_reset mode: {self.spk_reset}. Must be 'soft' or 'hard'.")
             spike_ = spike_no_grad > 0.
             # will be used in other place, like Delta Synapse, so stop its gradient
             if self.ref_var:
@@ -785,7 +785,7 @@ def update(self, x=None):
             elif self.spk_reset == 'hard':
                 V += (self.V_reset - V) * spike
             else:
-                raise ValueError
+                raise ValueError(f"Unknown spk_reset mode: {self.spk_reset}. Must be 'soft' or 'hard'.")
 
         else:
             spike = V >= self.V_th
@@ -1142,7 +1142,7 @@ def update(self, x=None):
             elif self.spk_reset == 'hard':
                 V += (self.V_reset - V) * spike_no_grad
             else:
-                raise ValueError
+                raise ValueError(f"Unknown spk_reset mode: {self.spk_reset}. Must be 'soft' or 'hard'.")
             spike_ = spike_no_grad > 0.
             # will be used in other place, like Delta Synapse, so stop its gradient
             if self.ref_var:
@@ -1497,7 +1497,7 @@ def update(self, x=None):
             elif self.spk_reset == 'hard':
                 V += (self.V_reset - V) * spike
             else:
-                raise ValueError
+                raise ValueError(f"Unknown spk_reset mode: {self.spk_reset}. Must be 'soft' or 'hard'.")
             w += self.b * spike
 
         else:
@@ -1843,7 +1843,7 @@ def update(self, x=None):
             elif self.spk_reset == 'hard':
                 V += (self.V_reset - V) * spike_no_grad
             else:
-                raise ValueError
+                raise ValueError(f"Unknown spk_reset mode: {self.spk_reset}. Must be 'soft' or 'hard'.")
             w += self.b * spike_no_grad
             spike_ = spike_no_grad > 0.
             # will be used in other place, like Delta Synapse, so stop its gradient
@@ -2142,7 +2142,7 @@ def update(self, x=None):
             elif self.spk_reset == 'hard':
                 V += (self.V_reset - V) * spike
             else:
-                raise ValueError
+                raise ValueError(f"Unknown spk_reset mode: {self.spk_reset}. Must be 'soft' or 'hard'.")
 
         else:
             spike = V >= self.V_th
@@ -2431,7 +2431,7 @@ def update(self, x=None):
             elif self.spk_reset == 'hard':
                 V += (self.V_reset - V) * spike_no_grad
             else:
-                raise ValueError
+                raise ValueError(f"Unknown spk_reset mode: {self.spk_reset}. Must be 'soft' or 'hard'.")
             spike_ = spike_no_grad > 0.
             # will be used in other place, like Delta Synapse, so stop its gradient
             if self.ref_var:
@@ -2734,7 +2734,7 @@ def update(self, x=None):
             elif self.spk_reset == 'hard':
                 V += (self.V_reset - V) * spike
             else:
-                raise ValueError
+                raise ValueError(f"Unknown spk_reset mode: {self.spk_reset}. Must be 'soft' or 'hard'.")
             w += self.b * spike
 
         else:
@@ -3054,7 +3054,7 @@ def update(self, x=None):
             elif self.spk_reset == 'hard':
                 V += (self.V_reset - V) * spike_no_grad
             else:
-                raise ValueError
+                raise ValueError(f"Unknown spk_reset mode: {self.spk_reset}. Must be 'soft' or 'hard'.")
             w += self.b * spike_no_grad
             spike_ = spike_no_grad > 0.
             # will be used in other place, like Delta Synapse, so stop its gradient
@@ -3417,7 +3417,7 @@ def update(self, x=None):
             elif self.spk_reset == 'hard':
                 V += (self.V_reset - V) * spike
             else:
-                raise ValueError
+                raise ValueError(f"Unknown spk_reset mode: {self.spk_reset}. Must be 'soft' or 'hard'.")
             I1 += spike * (self.R1 * I1 + self.A1 - I1)
             I2 += spike * (self.R2 * I2 + self.A2 - I2)
             V_th += (bm.maximum(self.V_th_reset, V_th) - V_th) * spike
@@ -3810,7 +3810,7 @@ def update(self, x=None):
             elif self.spk_reset == 'hard':
                 V += (self.V_reset - V) * spike_no_grad
             else:
-                raise ValueError
+                raise ValueError(f"Unknown spk_reset mode: {self.spk_reset}. Must be 'soft' or 'hard'.")
             I1 += spike * (self.R1 * I1 + self.A1 - I1)
             I2 += spike * (self.R2 * I2 + self.A2 - I2)
             V_th += (bm.maximum(self.V_th_reset, V_th) - V_th) * spike_no_grad
diff --git a/brainpy/dyn/synapses/abstract_models.py b/brainpy/dyn/synapses/abstract_models.py
index 0390fd2a..80f8ca84 100644
--- a/brainpy/dyn/synapses/abstract_models.py
+++ b/brainpy/dyn/synapses/abstract_models.py
@@ -285,7 +285,7 @@ def update(self, x):
 
         # update synaptic variables
         self.g.value, self.h.value = self.integral(self.g.value, self.h.value, share['t'], dt=share['dt'])
-        self.h += self.a * x
+        self.h.value = self.h.value + self.a * x
         return self.g.value
 
     def return_info(self):
@@ -552,7 +552,7 @@ def dg(self, g, t, h):
     def update(self, x):
         # update synaptic variables
         self.g.value, self.h.value = self.integral(self.g.value, self.h.value, share['t'], dt=share['dt'])
-        self.h += x
+        self.h.value = self.h.value + x
         return self.g.value
 
     def return_info(self):
@@ -737,7 +737,7 @@ def update(self, pre_spike):
         t = share.load('t')
         dt = share.load('dt')
         self.g.value, self.x.value = self.integral(self.g.value, self.x.value, t, dt=dt)
-        self.x += pre_spike
+        self.x.value = self.x.value + pre_spike
         return self.g.value
 
     def return_info(self):
diff --git a/brainpy/dynsys.py b/brainpy/dynsys.py
index 6d56e391..a27e9892 100644
--- a/brainpy/dynsys.py
+++ b/brainpy/dynsys.py
@@ -966,11 +966,18 @@ def _slice_to_num(slice_: slice, length: int):
     step = slice_.step
     if step is None:
         step = 1
+    if step == 0:
+        raise ValueError("slice step cannot be zero")
     # number
     num = 0
-    while start < stop:
-        start += step
-        num += 1
+    if step > 0:
+        while start < stop:
+            start += step
+            num += 1
+    else:
+        while start > stop:
+            start += step
+            num += 1
     return num
 
 
diff --git a/brainpy/helpers.py b/brainpy/helpers.py
index 8cdae877..5a7f7c62 100644
--- a/brainpy/helpers.py
+++ b/brainpy/helpers.py
@@ -116,6 +116,9 @@ def load_state(target: DynamicalSystem, state_dict: Dict, **kwargs):
     missing_keys = []
     unexpected_keys = []
     for name, node in nodes.items():
+        if name not in state_dict:
+            missing_keys.append(name)
+            continue
         r = node.load_state(state_dict[name], **kwargs)
         if r is not None:
             missing, unexpected = r
diff --git a/brainpy/integrators/ode/adaptive_rk.py b/brainpy/integrators/ode/adaptive_rk.py
index c22847b7..ee6864f3 100644
--- a/brainpy/integrators/ode/adaptive_rk.py
+++ b/brainpy/integrators/ode/adaptive_rk.py
@@ -67,6 +67,7 @@
 
 import jax.numpy as jnp
 
+from brainpy import _errors as errors
 from brainpy.integrators import constants as C, utils
 from brainpy.integrators.ode import common
 from brainpy.integrators.ode.base import ODEIntegrator
@@ -456,7 +457,7 @@ class BogackiShampine(AdaptiveRKIntegrator):
     A = [(),
          (0.5,),
          (0., 0.75),
-         ('2/9', '1/3', '4/0'), ]
+         ('2/9', '1/3', '4/9'), ]
     B1 = ['2/9', '1/3', '4/9', 0]
     B2 = ['7/24', 0.25, '1/3', 0.125]
     C = [0, 0.5, 0.75, 1]
diff --git a/brainpy/integrators/ode/generic.py b/brainpy/integrators/ode/generic.py
index 49924c06..8ee6c099 100644
--- a/brainpy/integrators/ode/generic.py
+++ b/brainpy/integrators/ode/generic.py
@@ -134,7 +134,7 @@ def set_default_odeint(method):
         raise ValueError(f'Unsupported ODE_INT numerical method: {method}.')
 
     global _DEFAULT_DDE_METHOD
-    _DEFAULT_ODE_METHOD = method
+    _DEFAULT_DDE_METHOD = method
 
 
 def get_default_odeint():
diff --git a/brainpy/math/ndarray.py b/brainpy/math/ndarray.py
index 7e486650..3b14e883 100644
--- a/brainpy/math/ndarray.py
+++ b/brainpy/math/ndarray.py
@@ -272,7 +272,7 @@ def value(self):
 
     @value.setter
     def value(self, value):
-        self_value = self._check_tracer()
+        self_value = self._value
 
         if isinstance(value, Array):
             value = value.value
diff --git a/brainpy/math/object_transform/base.py b/brainpy/math/object_transform/base.py
index 1f46973d..f6a6b976 100644
--- a/brainpy/math/object_transform/base.py
+++ b/brainpy/math/object_transform/base.py
@@ -773,7 +773,7 @@ def update(self, *args, **kwargs) -> 'NodeDict':
                     self[k] = v
             elif isinstance(arg, tuple):
                 assert len(arg) == 2
-                self[arg[0]] = args[1]
+                self[arg[0]] = arg[1]
         for k, v in kwargs.items():
             self[k] = v
         return self
@@ -781,8 +781,8 @@ def update(self, *args, **kwargs) -> 'NodeDict':
     def __setitem__(self, key, value) -> 'NodeDict':
         if self.check_unique:
             exist = self.get(key, None)
-            if id(exist) != id(value):
-                raise KeyError(f'Duplicate usage of key "{key}". "{key}" has been used for {value}.')
+            if exist is not None and id(exist) != id(value):
+                raise KeyError(f'Duplicate usage of key "{key}". "{key}" has been used for {exist}.')
         super().__setitem__(key, value)
         return self
 
diff --git a/brainpy/math/object_transform/variables.py b/brainpy/math/object_transform/variables.py
index f7d4d4c6..60671a14 100644
--- a/brainpy/math/object_transform/variables.py
+++ b/brainpy/math/object_transform/variables.py
@@ -109,7 +109,7 @@ def size_without_batch(self):
             return self.size
         else:
             sizes = self.size
-            return sizes[:self.batch_size] + sizes[self.batch_axis + 1:]
+            return sizes[:self.batch_axis] + sizes[self.batch_axis + 1:]
 
     @property
     def batch_axis(self) -> Optional[int]:
@@ -390,7 +390,7 @@ def update(self, *args, **kwargs) -> 'VarDict':
                     self[k] = v
             elif isinstance(arg, tuple):
                 assert len(arg) == 2
-                self[arg[0]] = args[1]
+                self[arg[0]] = arg[1]
         for k, v in kwargs.items():
             self[k] = v
         return self
diff --git a/brainpy/train/back_propagation.py b/brainpy/train/back_propagation.py
index a820dc48..332881e5 100644
--- a/brainpy/train/back_propagation.py
+++ b/brainpy/train/back_propagation.py
@@ -109,8 +109,8 @@ def __init__(
         '''
             )
         if seed is not None:
-            NoLongerSupportError('"seed" is no longer supported. '
-                                 'Please shuffle your data by yourself.')
+            raise NoLongerSupportError('"seed" is no longer supported. '
+                                       'Please shuffle your data by yourself.')
 
         # jit settings
         if isinstance(self._origin_jit, bool):
@@ -317,7 +317,7 @@ def fit(
                         fit_t1 = time.time()
                         aux = {}
                         for k, v in fit_epoch_metric.items():
-                            aux[k] = jnp.mean(bm.as_jax(bm.asarray(v)))
+                            aux[k] = np.mean(np.asarray(v))
                             if k not in report_train_metric:
                                 report_train_metric[k] = []
                                 detailed_train_metric[k] = []
@@ -420,7 +420,7 @@ def fit(
                         test_t1 = time.time()
                         aux = {}
                         for k, v in test_epoch_metric.items():
-                            aux[k] = jnp.mean(bm.as_jax(bm.asarray(v)))
+                            aux[k] = np.mean(np.asarray(v))
                             if k not in report_test_metric:
                                 report_test_metric[k] = []
                                 detailed_test_metric[k] = []
diff --git a/pyproject.toml b/pyproject.toml
index dc5164c3..40d1cb99 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -6,11 +6,10 @@ build-backend = "setuptools.build_meta"
 name = "brainpy"
 description = "BrainPy: Brain Dynamics Programming in Python"
 readme = "README.md"
-requires-python = ">=3.10"
+requires-python = ">=3.11"
 authors = [
     { name = "BrainPy Team", email = "chao.brain@qq.com" }
 ]
-license = { text = "GPL-3.0 license" }
 classifiers = [
     "Natural Language :: English",
     "Operating System :: OS Independent",
@@ -39,7 +38,7 @@ dependencies = [
     "jax",
     "tqdm",
     "brainstate>=0.2.7",
-    "brainunit",
+    "brainunit>=0.2.0",
     "brainevent>=0.0.7",
     "braintools>=0.0.9",
     'brainpy_state>=0.0.3',
diff --git a/requirements.txt b/requirements.txt
index b8e3db57..09fbf6cd 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,8 +1,8 @@
-numpy
+numpy>=1.15
 brainunit
 brainevent>=0.0.7
-braintools>=0.1.0
+braintools>=0.0.9
 brainstate>=0.2.7
-brainpy_state>=0.0.2
+brainpy_state>=0.0.3
 jax
 tqdm