ueue of data for the
        other protocol.  Eventually, C{pumpPolicy} will be called with one such
        queue and the corresponding protocol object.  The pump policy callable
        is responsible for emptying the queue and passing the strings it
        contains to the given protocol's C{dataReceived} method.  The signature
        of C{pumpPolicy} is C{(queue, protocol)}.  C{queue} is an object with a
        C{get} method which will return the next string written to the
        transport, or L{None} if the transport has been disconnected, and which
        evaluates to C{True} if and only if there are more items to be
        retrieved via C{get}.

    @return: A L{Deferred} which fires when the connection has been closed and
        both sides have received notification of this.
    )