'Overrides ``models.Field`` method. This is used to convert
bytes (from serialization etc) to an instance of this class'

def to_python(self, value):

    if (value is None):
        return None
    elif isinstance(value, oauth2client.client.Credentials):
        return value
    else:
        try:
            return jsonpickle.decode(base64.b64decode(encoding.smart_bytes(value)).decode())
        except ValueError:
            return pickle.loads(base64.b64decode(encoding.smart_bytes(value)))
