/usr/local/lib/swipl/library/ugraphs.pl
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 del_edges(+Graph, +Edges, -NewGraph)
Unify NewGraph with a new graph obtained by removing the list of Edges from Graph. Notice that no vertices are deleted. Example: 
?- del_edges([1-[3,5],2-[4],3-[],4-[5],5-[],6-[],7-[],8-[]],
             [1-6,2-3,3-2,5-7,3-2,4-5,1-3],
             NL).
NL = [1-[5],2-[4],3-[],4-[],5-[],6-[],7-[],8-[]]