[igraph] subtraction?

[Marco]

Hi all list!

Let's suppose I have a graph g, and a subgraph of g, let's call it h.
I'd like to build the graph that is defined of all the vertices in g
that are not in h.
Edges are kept the same as in g if both the endvertices survive, or
are deleted if at least one of the endvertices is killed.

How do it efficiently in igraph?

thanks in advance as always,

marco

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