def METHOD_NAME(self, conn: H2ClientProtocol, key: Tuple) -> H2ClientProtocol:
    self._connections[key] = conn
    # Now as we have established a proper HTTP/2 connection
    # we fire all the deferred's with the connection instance
    pending_requests = self._pending_requests.pop(key, None)
    while pending_requests:
        d = pending_requests.popleft()
        d.callback(conn)
    return conn