Send request

        Args:
            resource: resource
            action: action
            data: string or object which can be json.dumps
            headers: http headers

def _request(self, resource, action, data=None, headers=None):
        """
        Send request

        Args:
            resource: resource
            action: action
            data: string or object which can be json.dumps
            headers: http headers
        """
        url, httpmethod = res_to_url(resource, action)
        return self.ajax(url, httpmethod, data, headers)