(assert (or (null edge-class)
(subtypep edge-class (directed-edge-class graph))
(subtypep edge-class (undirected-edge-class graph))) nil
"Edge-class must be nil or a subtype of ~A or ~A"
(undirected-edge-class graph)
(directed-edge-class graph))
(assert (or (null edge-class)
(subtypep edge-class (directed-edge-class graph))
(subtypep edge-class (undirected-edge-class graph))) nil
"Edge-class must be nil or a subtype of ~A or ~A"
(undirected-edge-class graph)
(directed-edge-class graph))