Writes messages that should go to the client to the db.

def WriteClientActionRequests(self, requests):
    """Writes messages that should go to the client to the db."""
    for r in requests:
      req_dict = self.flow_requests.get((r.client_id, r.flow_id), {})
      if r.request_id not in req_dict:
        request_keys = [(r.client_id, r.flow_id, r.request_id) for r in requests
                       ]
        raise db.AtLeastOneUnknownRequestError(request_keys)

    for r in requests:
      request_key = (r.client_id, r.flow_id, r.request_id)
      self.client_action_requests[request_key] = r