def _parse_bool_default_value(property_name, default_value_string):
    """Parse and return the default value for a boolean property."""
    lowercased_value_string = default_value_string.lower()
    if lowercased_value_string in {"0", "false"}:
        return False
    elif lowercased_value_string in {"1", "true"}:
        return True
    else:
        raise AssertionError(
            'Unsupported default value for boolean property "{}": '
            "{}".format(property_name, default_value_string)
        )