changeEdgeLabel :: Label -> Id -> GS Edge
changeEdgeLabel l i = getEdgeByIdUnsafe i >>= changeEdgeLabelE l
changeEdgeLabel :: Label -> Id -> GS Edge
changeEdgeLabel l i = getEdgeByIdUnsafe i >>= changeEdgeLabelE l
changeEdgeLabel l i = getEdgeByIdUnsafe i >>= changeEdgeLabelE l