Asserts that two xml documents are equal.
    :param first: first etree object or xml string
    :param second: second etree object or xml string
    :param check_tags_order: if False, the order of children is ignored
    :return: raises AssertionError if documents are not equal

def assert_xml_equal(first, second, check_tags_order=False):
    """
    Asserts that two xml documents are equal.
    :param first: first etree object or xml string
    :param second: second etree object or xml string
    :param check_tags_order: if False, the order of children is ignored
    :return: raises AssertionError if documents are not equal
    """
    _assert_xml_compare(_assert_xml_docs_are_equal, first, second, check_tags_order=check_tags_order)