code: def _validate_callback(callback):
          
  
          cb_name = callback.__name__ if hasattr(callback, "__name__") else callback
          if not callable(callback):
              msg = "The specified callback '{}' is not callable.".format(cb_name)
              raise client_err.SlackClientError(msg)
          callback_params = inspect.signature(callback).parameters.values()
          if not any(
              param for param in callback_params if param.kind == param.VAR_KEYWORD
          ):
              msg = "The callback '{}' must accept keyword arguments (**kwargs).".format(
                  cb_name
              )
              raise client_err.SlackClientError(msg)
docs: Checks if the specified callback is callable and accepts a kwargs param.
  
          Args:
              callback (obj): Any object or a list of objects that can be called.
                  e.g. <function say_hello at 0x101234567>
  
          Raises:
              SlackClientError: The specified callback is not callable.
              SlackClientError: The callback must accept keyword arguments (**kwargs).