Gets a list of users who have updated their device identity keys.

        Args:
            from_token (str): The desired start point of the list. Should be the
                next_batch field from a response to an earlier call to /sync.
            to_token (str): The desired end point of the list. Should be the next_batch
                field from a recent call to /sync - typically the most recent such call.

def key_changes(self, from_token, to_token):
        """Gets a list of users who have updated their device identity keys.

        Args:
            from_token (str): The desired start point of the list. Should be the
                next_batch field from a response to an earlier call to /sync.
            to_token (str): The desired end point of the list. Should be the next_batch
                field from a recent call to /sync - typically the most recent such call.
        """
        params = {"from": from_token, "to": to_token}
        return self._send("GET", "/keys/changes", query_params=params)