Returns the neighbors of a given site using a specific neighbor-finding
    method.

    Args:
        struct (Structure): input structure.
        n (int): index of site in Structure object for which motif type
                is to be determined.
        approach (str): type of neighbor-finding approach, where
              "min_dist" will use the MinimumDistanceNN class,
              "voronoi" the VoronoiNN class, "min_OKeeffe" the
              MinimumOKeeffe class, and "min_VIRE" the MinimumVIRENN class.
        delta (float): tolerance involved in neighbor finding.
        cutoff (float): (large) radius to find tentative neighbors.

    Returns: neighbor sites.

def get_neighbors_of_site_with_index(struct, n, approach="min_dist", delta=0.1, \
                                     cutoff=10.0):
    """
    Returns the neighbors of a given site using a specific neighbor-finding
    method.

    Args:
        struct (Structure): input structure.
        n (int): index of site in Structure object for which motif type
                is to be determined.
        approach (str): type of neighbor-finding approach, where
              "min_dist" will use the MinimumDistanceNN class,
              "voronoi" the VoronoiNN class, "min_OKeeffe" the
              MinimumOKeeffe class, and "min_VIRE" the MinimumVIRENN class.
        delta (float): tolerance involved in neighbor finding.
        cutoff (float): (large) radius to find tentative neighbors.

    Returns: neighbor sites.
    """

    if approach == "min_dist":
        return MinimumDistanceNN(tol=delta, cutoff=cutoff).get_nn(
            struct, n)
    elif approach == "voronoi":
        return VoronoiNN(tol=delta, cutoff=cutoff).get_nn(
            struct, n)
    elif approach == "min_OKeeffe":
        return MinimumOKeeffeNN(tol=delta, cutoff=cutoff).get_nn(
            struct, n)
    elif approach == "min_VIRE":
        return MinimumVIRENN(tol=delta, cutoff=cutoff).get_nn(
            struct, n)
    else:
        raise RuntimeError("unsupported neighbor-finding method ({}).".format(
            approach))