A clique in an undirected graph G = (V, E) is a subset of the vertex set such that for every two vertices in C there exists an edge connecting the two.

maximum_clique(G[, sampler, lagrange]) Returns an approximate maximum clique.
clique_number(G[, sampler, lagrange]) Returns the number of vertices in the maximum clique of a graph.
is_clique(G, clique_nodes) Determines whether the given nodes form a clique.