'Constructor for a BatchHttpRequest.
Args:
callback: callable, A callback to be called for each response, of the
form callback(id, response, exception). The first parameter is the
request id, and the second is the deserialized response object. The
third is an googleapiclient.errors.HttpError exception object if an HTTP error
occurred while processing the request, or None if no error occurred.
batch_uri: string, URI to send batch requests to.'

@util.positional(1)
def __init__(self, callback=None, batch_uri=None):

    if (batch_uri is None):
        batch_uri = 'https://www.googleapis.com/batch'
    self._batch_uri = batch_uri
    self._callback = callback
    self._requests = {}
    self._callbacks = {}
    self._order = []
    self._last_auto_id = 0
    self._base_id = None
    self._responses = {}
    self._refreshed_credentials = {}
