Error when register_model() Custom model

I am encountering an issue while trying to build my own model following the guide provided in the documentation(https://federatedscope.io/docs/own-case/). Unfortunately, it seems that the `register `function for my custom model is not taking effect.

I did not install the library using `pip install .`, but instead, I am running the code directly from the source. I have set `DEV_MODE = True ` in the main function as recommended.

While I was able to successfully register my custom data using the `register` function, I ran into a problem with registering my custom model. Upon stepping through the code, I noticed that only the preset models (like fedsam_conv2, resnet, and mynet) were registered in `register.model_dict`, but my custom model was not.
```jsx
for func in register.model_dict.values():
model = func(model_config, input_shape)
if model is not None:
return model
register_model("FS-Net", call_fs_net)
```

My data `register` function `register_data("ISCX", call_file_data)` can be executed, but `register_model("FS-Net", call_fs_net)` is not executed.Here is a version of the relevant code I am using:

```jsx
def call_fs_net(model_config, local_data):
if model_config.type == "FS-Net":
model = ModelBuilder(model_config)
return model

register_model("FS-Net", call_fs_net)
```

I would greatly appreciate any guidance or suggestions you could provide to help me resolve this issue. Thank you for your time and support!

Start with the own-case documentation and the register_model entry point, then compare how register_data adds entries to the registry with how register.model_dict is populated. Confirm why call_fs_net is not present and verify that the custom model can be selected and constructed when registration is working.

Written by the indexing model from the issue text.