'Return the contents on link.'

def link_contents(self, link):

    (node, channel) = (link.source_node, link.source_channel)
    if (node in self._node_outputs):
        return self._node_outputs[node][channel]
    else:
        pending = [sig for sig in self._input_queue if (sig.link is link)]
        return {sig.id: sig.value for sig in pending}
