def ecp_pots_are_subset(subset, superset, compare_meta=False, rel_tol=0.0):
    '''
    Determine if a list of ecp potentials is a subset of another

    If 'subset' is a subset of the 'superset', True is returned.

    The potentials are compared approximately (exponents/coefficients are 
    within a tolerance)

    If compare_meta is True, the metadata is also compared for exact equality. 
    '''

    for item1 in subset:
        for item2 in superset:
            if compare_ecp_pots(item1, item2, compare_meta, rel_tol):
                break
        else:
            return False

    return True
Determine if a list of ecp potentials is a subset of another

    If 'subset' is a subset of the 'superset', True is returned.

    The potentials are compared approximately (exponents/coefficients are 
    within a tolerance)

    If compare_meta is True, the metadata is also compared for exact equality.