code: def min_maximal_matching(G):
      r"""Returns the minimum maximal matching of G. That is, out of all maximal
      matchings of the graph G, the smallest is returned.
  
      Parameters
      ----------
      G : NetworkX graph
        Undirected graph
  
      Returns
      -------
      min_maximal_matching : set
        Returns a set of edges such that no two edges share a common endpoint
        and every edge not in the set shares some common endpoint in the set.
        Cardinality will be 2*OPT in the worst case.
  
      Notes
      -----
      The algorithm computes an approximate solution for the minimum maximal
      cardinality matching problem. The solution is no more than 2 * OPT in size.
      Runtime is $O(|E|)$.
  
      References
      ----------
      .. [1] Vazirani, Vijay Approximation Algorithms (2001)
      """
      return nx.maximal_matching(G)
  
label_desc: Use image node_id 1 for calling a global function with example usage: min_maximal_matching(G) and returns: nx