code: def _resolve_method(self, request):
          # type: (ApiClientRequest) -> Callable
          
          try:
              return getattr(requests, request.method.lower())
          except AttributeError:
              raise ApiClientException(
                  "Invalid request method: {}".format(request.method))
docs: Resolve the method from request object to `requests` http
          call.
  
          :param request: Request to dispatch to the ApiClient
          :type request: ApiClientRequest
          :return: The HTTP method that maps to the request call.
          :rtype: Callable
          :raises :py:class:`ask_sdk_core.exceptions.ApiClientException`
              if invalid http request method is being called