Use this if you are using igraph from R
Check whether a given set of vertices is a vertex separator.
The input graph. It may be directed, but edge directions are ignored.
A numeric vector giving the vertex ids of the candidate separator.
is_separator decides whether the supplied vertex set is a vertex
separator. A vertex set is a vertex separator if its removal results a
In the special case of a fully connected graph with n vertices, each set of n-1 vertices is considered to be a vertex separator.
A logical scalar, whether the supplied vertex set is a (minimal) vertex separator or not.