Construct an edge.
Returns the other node of this edge.
Returns the node that is common to this and other.
Orders edge lexicographically by start, end.
Two edges are equal iff their incident nodes are the same.
Returns the other node of this edge.
Get the end of this edge, i.e. the larger of both incident nodes.
Get the start of this edge, i.e. the smaller of both incident nodes.