def add(self, request, callback=None, request_id=None):
    """Add a new request.

    Every callback added will be paired with a unique id, the request_id. That
    unique id will be passed back to the callback when the response comes back
    from the server. The default behavior is to have the library generate it's
    own unique id. If the caller passes in a request_id then they must ensure
    uniqueness for each request_id, and if they are not an exception is
    raised. Callers should either supply all request_ids or nevery supply a
    request id, to avoid such an error.

    Args:
      request: HttpRequest, Request to add to the batch.
      callback: callable, A callback to be called for this response, of the
        form callback(id, response). The first parameter is the request id, and
        the second is the deserialized response object.
      request_id: string, A unique id for the request. The id will be passed to
        the callback with the response.

    Returns:
      None

    Raises:
      BatchError if a resumable request is added to a batch.
      KeyError is the request_id is not unique.
    """
    if request_id is None:
      request_id = self._new_id()
    if request.resumable is not None:
      raise BatchError("Resumable requests cannot be used in a batch request.")
    if request_id in self._requests:
      raise KeyError(request_id % "A request with this ID already exists: %s")
    self._requests[request_id] = (request, callback)
    self._order.append(request_id)
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/google-api-python-client/apiclient/http.py/BatchHttpRequest.add/swapped operands of `%`