docs: def _rm_is_alignment_line(parts, s1_name, s2_name):
    """
    return true if the tokenized line is a repeatmasker alignment line.
  
    :param parts:   the line, already split into tokens around whitespace
    :param s1_name: the name of the first sequence, as extracted from the header
                    of the element this line is in
    :param s2_name: the name of the second sequence, as extracted from the header
                    of the element this line is in
    """
    if len(parts) < 2:
      return False
    if _rm_name_match(parts[0], s1_name):
      return True
    if (_rm_name_match(parts[0], s2_name) or
       (parts[0] == "C" and _rm_name_match(parts[1], s2_name))):
      return True
    return False