Tests if all fractional coords in subset are contained in superset.

    Args:
        subset, superset: List of fractional coords
        atol (float or size 3 array): Tolerance for matching
        mask (boolean array): Mask of matches that are not allowed.
            i.e. if mask[1,2] == True, then subset[1] cannot be matched
            to superset[2]

    Returns:
        True if all of subset is in superset.

def is_coord_subset_pbc(subset, superset, atol=1e-8, mask=None):
    """
    Tests if all fractional coords in subset are contained in superset.

    Args:
        subset, superset: List of fractional coords
        atol (float or size 3 array): Tolerance for matching
        mask (boolean array): Mask of matches that are not allowed.
            i.e. if mask[1,2] == True, then subset[1] cannot be matched
            to superset[2]

    Returns:
        True if all of subset is in superset.
    """
    c1 = np.array(subset, dtype=np.float64)
    c2 = np.array(superset, dtype=np.float64)
    if mask is not None:
        m = np.array(mask, dtype=np.int)
    else:
        m = np.zeros((len(subset), len(superset)), dtype=np.int)
    atol = np.zeros(3, dtype=np.float64) + atol
    return cuc.is_coord_subset_pbc(c1, c2, atol, m)