Update docs

docs/sphinx_doc/en/source/tutorial/203-model.md

@@ -566,6 +566,7 @@ The new model wrapper class should
 - inherit from `ModelWrapperBase` class,
 - provide a `model_type` field to identify this model wrapper in the model configuration, and
 - implement its `__init__` and `__call__` functions.
+- register the new model wrapper class by calling `agentscope.register_model_wrapper_class` function
 
 The following is an example for creating a new model wrapper class.
 
@@ -586,10 +587,13 @@ class MyModelWrapper(ModelWrapperBase):
         # ...
 ```
 
-After creating the new model wrapper class, the model wrapper will be registered into AgentScope automatically.
-You can use it in the model configuration directly.
+Then we register the new model wrapper class and use it in the model configuration.
 
 ```python
+import agentscope
+
+agentscope.register_model_wrapper_class(MyModelWrapper)
+
 my_model_config = {
     # Basic parameters
     "config_name": "my_model_config",

docs/sphinx_doc/zh_CN/source/tutorial/203-model.md

@@ -586,6 +586,7 @@ AgentScope允许开发者自定义自己的模型包装器。新的模型包装
 - 继承自`ModelWrapperBase`类，
 - 提供`model_type`字段以在模型配置中标识这个Model Wrapper类，并
 - 实现`__init__`和`__call__`函数。
+- 调用`agentscope.register_model_wrapper_class`函数，将其注册到AgentScope中。
 
 ```python
 from agentscope.models import ModelWrapperBase
@@ -604,10 +605,13 @@ class MyModelWrapper(ModelWrapperBase):
         # ...
 ```
 
-在创建新的模型包装器类之后，模型包装器将自动注册到AgentScope中。
-您可以直接在模型配置中使用它。
+然后调用`register_model_wrapper_class`函数将其注册到AgentScope中。
 
 ```python
+import agentscope
+
+agentscope.register_model_wrapper_class(MyModelWrapper)
+
 my_model_config = {
     # 基础参数
     "config_name": "my_model_config",