6.6. igraph_es_fromto — Edge selector, all edges between two vertex sets.

int igraph_es_fromto(igraph_es_t *es,
		     igraph_vs_t from, igraph_vs_t to);

This function is not implemented yet.

Arguments:

`es`:	Pointer to an uninitialized edge selector.
`from`:	Vertex selector, their outgoing edges will be selected.
`to`:	Vertex selector, their incoming edges will be selected from the previous selection.

Returns:

Error code.

Time complexity: O(1).