Description: The edges of a graph represented as ordered pair, shown as operation
value. Although a little less intuitive, this representation is often
used because it is shorter than the representation as function value of a
graph given as ordered pair, see edgopval . The representation
ran E for the set of edges is even shorter, though. (Contributed by AV, 2-Jan-2020)(Revised by AV, 13-Oct-2020)