code: def maximum_independent_set(G):
      """Returns an approximate maximum independent set.
  
      Independent set or stable set is a set of vertices in a graph, no two of
      which are adjacent. That is, it is a set I of vertices such that for every
      two vertices in I, there is no edge connecting the two. Equivalently, each
      edge in the graph has at most one endpoint in I. The size of an independent
      set is the number of vertices it contains [1]_.
  
      A maximum independent set is a largest independent set for a given graph G
      and its size is denoted $\\alpha(G)$. The problem of finding such a set is called
      the maximum independent set problem and is an NP-hard optimization problem.
      As such, it is unlikely that there exists an efficient algorithm for finding
      a maximum independent set of a graph.
  
      The Independent Set algorithm is based on [2]_.
  
      Parameters
      ----------
      G : NetworkX graph
          Undirected graph
  
      Returns
      -------
      iset : Set
          The apx-maximum independent set
  
      Examples
      --------
      >>> G = nx.path_graph(10)
      >>> nx.approximation.maximum_independent_set(G)
      {0, 2, 4, 6, 9}
  
      Raises
      ------
      NetworkXNotImplemented
          If the graph is directed or is a multigraph.
  
      Notes
      -----
      Finds the $O(|V|/(log|V|)^2)$ apx of independent set in the worst case.
  
      References
      ----------
      .. [1] `Wikipedia: Independent set
          <https://en.wikipedia.org/wiki/Independent_set_(graph_theory)>`_
      .. [2] Boppana, R., & Halldórsson, M. M. (1992).
         Approximating maximum independent sets by excluding subgraphs.
         BIT Numerical Mathematics, 32(2), 180–196. Springer.
      """
      iset, _ = clique_removal(G)
      return iset
  
imports: import networkx
  from networkx.algorithms.approximation import ramsey
  from networkx.utils import not_implemented_for
label_desc: Use image node_id 1 for calling a global function with example usage: maximum_independent_set(G) and returns: iset