I did that, see https://trac.sagemath.org/ticket/18545 , but now I am unsure aftera a comment from Kevin.
-- Jori Mäntysalo
Graphs have vertices and edges, posets have elements and relations. This
is of course mirrored to function names, like .cover_relations() instead
of .edges(). Should we mirror that to parameter names in plot() and show()
also?
