'Return True if the current auth token is already cached and hasn\'t
expired yet.
:return: ``True`` if the token is still valid, ``False`` otherwise.
:rtype: ``bool``'

def is_token_valid(self):

    if (not self.auth_token):
        return False
    if (not self.auth_token_expires):
        return False
    expires = (self.auth_token_expires - datetime.timedelta(seconds=AUTH_TOKEN_EXPIRES_GRACE_SECONDS))
    time_tuple_expires = expires.utctimetuple()
    time_tuple_now = datetime.datetime.utcnow().utctimetuple()
    if (time_tuple_now < time_tuple_expires):
        return True
    return False
