def parse_special_header(self, linenum, info):
        """
        Parses part of a diff beginning at the specified line number, trying
        to find a special diff header. This usually occurs before the standard
        diff header.

        The line number returned is the line after the special header,
        which can be multiple lines long.
        """
        if linenum + 1 < len(self.lines) and \
           self.lines[linenum].startswith(b"Index: ") and \
           self.lines[linenum + 1] == self.INDEX_SEP:
            # This is an Index: header, which is common in CVS and Subversion,
            # amongst other systems.
            try:
                info['index'] = self.lines[linenum].split(None, 1)[1]
            except __HOLE__:
                raise DiffParserError("Malformed Index line", linenum)
            linenum += 2

        return linenum
dataset/ETHPy150Open reviewboard/reviewboard/reviewboard/diffviewer/parser.py/DiffParser.parse_special_header