def maximum_independent_set(G, sampler=None, lagrange=2.0, **sampler_args):
    """Returns an approximate maximum independent set.

    Defines a QUBO with ground states corresponding to a
    maximum independent set and uses the sampler to sample from
    it.

    An independent set is a set of nodes such that the subgraph
    of G induced by these nodes contains no edges. A maximum
    independent set is an independent set of largest possible size.

    Parameters
    ----------
    G : NetworkX graph
        The graph on which to find a maximum cut independent set.

    sampler
        A binary quadratic model sampler. A sampler is a process that
        samples from low energy states in models defined by an Ising
        equation or a Quadratic Unconstrained Binary Optimization
        Problem (QUBO). A sampler is expected to have a 'sample_qubo'
        and 'sample_ising' method. A sampler is expected to return an
        iterable of samples, in order of increasing energy. If no
        sampler is provided, one must be provided using the
        `set_default_sampler` function.
        
    lagrange : optional (default 2)
        Lagrange parameter to weight constraints (no edges within set) 
        versus objective (largest set possible).

    sampler_args
        Additional keyword parameters are passed to the sampler.

    Returns
    -------
    indep_nodes : list
       List of nodes that form a maximum independent set, as
       determined by the given sampler.

    Example
    -------
    This example uses a sampler from
    `dimod <https://github.com/dwavesystems/dimod>`_ to find a maximum
    independent set for a graph of a Chimera unit cell created using the
    `chimera_graph()` function.

    >>> import dimod
    >>> sampler = dimod.SimulatedAnnealingSampler()
    >>> G = dnx.chimera_graph(1, 1, 4)
    >>> indep_nodes = dnx.maximum_independent_set(G, sampler)

    Notes
    -----
    Samplers by their nature may not return the optimal solution. This
    function does not attempt to confirm the quality of the returned
    sample.

    References
    ----------

    `Independent Set on Wikipedia <https://en.wikipedia.org/wiki/Independent_set_(graph_theory)>`_

    `QUBO on Wikipedia <https://en.wikipedia.org/wiki/Quadratic_unconstrained_binary_optimization>`_

    .. [AL] Lucas, A. (2014). Ising formulations of many NP problems.
       Frontiers in Physics, Volume 2, Article 5.

    """
    return maximum_weighted_independent_set(G, None, sampler, lagrange, **sampler_args)