is mentioned by

Def adjl-edge-accum(A;s',x'.f(s';x');s;x) == list_accum(s',x'.f(s';x');s;A.out(x))	[adjl-edge-accum]
Def adjl-graph(G) == < vertices = G.size, edges = x:G.size||G.out(x)||, incidence = e. < 1of(e),(G.out(1of(e)))[2of(e)] > >	[adjl-graph]

Try larger context: Graphs