code: def handle_authn_request(self, context, binding_in):
          
          return self._handle_authn_request(context, binding_in, self.idp)
docs: This method is bound to the starting endpoint of the authentication.
  
          :type context: satosa.context.Context
          :type binding_in: str
          :rtype: satosa.response.Response
  
          :param context: The current context
          :param binding_in: The binding type (http post, http redirect, ...)
          :return: response