code: def _generatePayload(self, query):
          
          payload = self._payload_default.copy()
          if query:
              payload.update(query)
          payload["__req"] = str_base(self._req_counter, 36)
          payload["seq"] = self._seq
          self._req_counter += 1
          return payload
docs: Adds the following defaults to the payload:
            __rev, __user, __a, ttstamp, fb_dtsg, __req