Could any body tell me why the validation form methods don't be called automatically(don't work at all)?

Rasa Open Source
28 

(rasa-chatbot3.8) D:\master-linux\salama4ai-chatbot>rasa run actions
2022-02-20 12:12:15 INFO     rasa_sdk.endpoint  - Starting action endpoint server...
2022-02-20 12:12:15 INFO     rasa_sdk.executor  - Registered function for 'action_answer'.
2022-02-20 12:12:15 INFO     rasa_sdk.executor  - Registered function for 'validate_country_pop_cap_form'.
2022-02-20 12:12:15 INFO     rasa_sdk.endpoint  - Action endpoint is up and running on http://0.0.0.0:5055
validate_country
Exception occurred while handling uri: 'http://localhost:5055/webhook'
Traceback (most recent call last):
  File "handle_request", line 83, in handle_request
    class Sanic(BaseSanic, metaclass=TouchUpMeta):
  File "C:\Users\huzyfa\Anaconda3\envs\rasa-chatbot3.8\lib\site-packages\rasa_sdk\endpoint.py", line 104, in webhook
    result = await executor.run(action_call)
  File "C:\Users\huzyfa\Anaconda3\envs\rasa-chatbot3.8\lib\site-packages\rasa_sdk\executor.py", line 397, in run
    events = await utils.call_potential_coroutine(
  File "C:\Users\huzyfa\Anaconda3\envs\rasa-chatbot3.8\lib\site-packages\rasa_sdk\utils.py", line 230, in call_potential_coroutine
    return await coroutine_or_return_value
  File "C:\Users\huzyfa\Anaconda3\envs\rasa-chatbot3.8\lib\site-packages\rasa_sdk\forms.py", line 46, in run
    validation_events = await self._extract_validation_events(
  File "C:\Users\huzyfa\Anaconda3\envs\rasa-chatbot3.8\lib\site-packages\rasa_sdk\forms.py", line 265, in _extract_validation_events
    validation_events = await self.get_validation_events(
  File "C:\Users\huzyfa\Anaconda3\envs\rasa-chatbot3.8\lib\site-packages\rasa_sdk\forms.py", line 167, in get_validation_events
    validate_method(slot_value, dispatcher, tracker, domain)
  File "D:\master-linux\salama4ai-chatbot\actions\actions.py", line 48, in validate_country
    country = slot_value.title()
AttributeError: 'dict' object has no attribute 'title'