def METHOD_NAME(self, lines: list[str]) -> list[str]:
    """
    Xml_Importer.preprocess_lines.
    Ensure that closing tags are followed by a newline.
    Importer.import_from_string calls this method before generating lines.
    """
    def repl(m: re.Match) -> str:
        """
            Split lines, adding leading whitespace to the second line.
            *Don't* separate tags if the tags open and close the same element.
        """
        m2 = self.tag_name_pat.match(m.group(2))
        m3 = self.tag_name_pat.match(m.group(3))
        tag_name2 = m2 and m2.group(1) or ''
        tag_name3 = m3 and m3.group(1) or ''
        same_element = (
            tag_name2 == tag_name3
            and not m.group(2).startswith('</')
            and m.group(3).startswith('</')
        )
        lws = g.get_leading_ws(m.group(1))
        sep = '' if same_element else '\n' + lws
        return m.group(1) + m.group(2).rstrip() + sep + m.group(3)
    result_lines = []
    for i, line in enumerate(lines):
        s = re.sub(self.adjacent_tags_pat, repl, line)
        result_lines.extend(g.splitLines(s))
    return result_lines