code: void disconnectEdgeFromCluster_(int edge, int cluster) {
  		int next = getNextEdge(edge, cluster);
  		assert (getPrevEdge(next, cluster) == edge);
  		int prev = getPrevEdge(edge, cluster);
  		assert (getNextEdge(prev, cluster) == edge);
  		int first_edge = getClusterFirstEdge(cluster);
  		if (next != edge) {
  			setNextEdge_(prev, cluster, next);
  			setPrevEdge_(next, cluster, prev);
  			if (first_edge == edge)
  				setClusterFirstEdge_(cluster, next);
  		} else
  			setClusterFirstEdge_(cluster, -1);
  	}
docs: Disconnects the edge from a cluster it is connected to.