is-matching? (clj)

Decides whether the given set represents a valid matching in G. A *matching* in a graph is a set of edges in which no two distinct edges share a common endpoint. Parameters ---------- `g` : graph `matching` : set A set representing a matching. It must have elements of the form #{u v}, where [u v] is an edge in the matching. Returns ------- boolean Whether the given set represents a valid matching in the graph.