Return a Python dict containing the important information
        about this Session Token.

def to_dict(self):
        """
        Return a Python dict containing the important information
        about this Session Token.
        """
        return {'access_key': self.access_key,
                'secret_key': self.secret_key,
                'session_token': self.session_token,
                'expiration': self.expiration,
                'request_id': self.request_id}