def DeleteFlowRequests(self, requests):
    """Deletes a list of flow requests from the database."""
    for request in requests:
      if (request.client_id, request.flow_id) not in self.flows:
        raise db.UnknownFlowError(request.client_id, request.flow_id)

    for request in requests:
      key = (request.client_id, request.flow_id)
      request_dict = self.flow_requests.get(key, {})
      try:
        del request_dict[request.request_id]
      except KeyError:
        raise db.UnknownFlowRequestError(request.client_id, request.flow_id,
                                         request.request_id)

      response_dict = self.flow_responses.get(key, {})
      try:
        del response_dict[request.request_id]
      except KeyError:
        pass