def low_balances(spec):
    """
    Helper method to create a series of low balances.
    Usage: `@with_custom_state(balances_fn=low_balances, ...)`
    """
    num_validators = spec.SLOTS_PER_EPOCH * 8
    # Technically the balances cannot be this low starting from genesis, but it is useful for testing
    low_balance = 18 * 10 ** 9
    return [low_balance] * num_validators