def sockets(self):
        """
        Returns a tuple of sockets connected to the pty (stdin,stdout,stderr).

        If any of the sockets are not attached in the container, `None` is
        returned in the tuple.
        """

        info = self._container_info()

        def attach_socket(key):
            if info['Config']['Attach{0}'.format(key.capitalize())]:
                socket = self.client.attach_socket(
                    self.container,
                    {key: 1, 'stream': 1, 'logs': self.logs},
                )
                stream = io.Stream(socket)

                if info['Config']['Tty']:
                    return stream
                else:
                    return io.Demuxer(stream)
            else:
                return None

        return map(attach_socket, ('stdin', 'stdout', 'stderr'))
Returns a tuple of sockets connected to the pty (stdin,stdout,stderr).

        If any of the sockets are not attached in the container, `None` is
        returned in the tuple.