code: def rank(self):
          
          max_rank = 0
          
          for each in self.hyperedges():
              if len(self.edge_links[each]) > max_rank:
                  max_rank = len(self.edge_links[each])
                  
          return max_rank
docs: Return the rank of the given hypergraph.
          
          @rtype:  int
          @return: Rank of graph.