let G1 be _Graph; :: thesis: for G2 being removeDParallelEdges of G1 holds
( G1 is chordal iff G2 is chordal )
let G2 be removeDParallelEdges of G1; :: thesis: ( G1 is chordal iff G2 is chordal )
set G3 = the removeParallelEdges of G2;
the removeParallelEdges of G2 is removeParallelEdges of G1 by Th95;
then ( G1 is chordal iff the removeParallelEdges of G2 is chordal ) by Th106;
hence ( G1 is chordal iff G2 is chordal ) by Th106; :: thesis: verum