Gather the ids of the plotting handles attached to this callback
        This allows checking that a stream is not given the state
        of a plotting handle it wasn't attached to

def _get_stream_handle_ids(self, handles):
        """
        Gather the ids of the plotting handles attached to this callback
        This allows checking that a stream is not given the state
        of a plotting handle it wasn't attached to
        """
        stream_handle_ids = defaultdict(dict)
        for stream in self.streams:
            for h in self.models:
                if h in handles:
                    handle_id = handles[h].ref['id']
                    stream_handle_ids[stream][h] = handle_id
        return stream_handle_ids