Class Credentials

Take an httplib2.Http instance (or equivalent) and authorizes it.

Authorizes it for the set of credentials, usually by replacing
http.request() with a method that adds in the appropriate headers and then
delegates to the original Http.request() method.

Args:
  http: httplib2.Http, an http object to be used to make the refresh
    request.

Forces a refresh of the access_token.

Args:
  http: httplib2.Http, an http object to be used to make the refresh
    request.

Revokes a refresh_token and makes the credentials void.

Args:
  http: httplib2.Http, an http object to be used to make the revoke
    request.

Add the authorization to the headers.

Args:
  headers: dict, the headers to add the Authorization header to.

Creating a JSON representation of an instance of Credentials.

Returns:
   string, a JSON representation of this instance, suitable to pass to
   from_json().

Utility class method to instantiate a Credentials subclass from a JSON
representation produced by to_json().

Args:
  s: string, JSON from to_json().

Returns:
  An instance of the subclass of Credentials that was serialized with
  to_json().

Instantiate a Credentials object from a JSON description of it.

The JSON should have been produced by calling .to_json() on the object.

Args:
  data: dict, A deserialized JSON object.

Returns:
  An instance of a Credentials subclass.