-- | updates a typed graph morphism, mapping edge e1 to edge e2. It assumes both edges already exist.
updateEdgeRelation :: EdgeId -> EdgeId -> TypedGraphMorphism a b -> TypedGraphMorphism a b
updateEdgeRelation e1 e2 tgm =
  tgm { mapping = GM.updateEdgeRelation e1 e2 (mapping tgm) }
updateEdgeRelation :: EdgeId -> EdgeId -> TypedGraphMorphism a b -> TypedGraphMorphism a b
updateEdgeRelation e1 e2 tgm =
  tgm { mapping = GM.updateEdgeRelation e1 e2 (mapping tgm) }
updateEdgeRelation e1 e2 tgm =
  tgm { mapping = GM.updateEdgeRelation e1 e2 (mapping tgm) }