How to use the unidiff.constants.RE_RENAME_SOURCE_FILENAME.match function in unidiff

def _parse(self, diff, encoding):
        current_file = None
        patch_info = None

        diff = enumerate(diff, 1)
        for unused_diff_line_no, line in diff:
            if encoding is not None:
                line = line.decode(encoding)

            # check for a git rename, source file
            is_rename_source_filename = RE_RENAME_SOURCE_FILENAME.match(line)
            if is_rename_source_filename:
                # prefix with 'a/' to match expected git source format
                source_file = (
                    'a/' + is_rename_source_filename.group('filename'))
                # keep line as patch_info
                patch_info.append(line)
                # reset current file
                current_file = None
                continue

            # check for a git rename, target file
            is_rename_target_filename = RE_RENAME_TARGET_FILENAME.match(line)
            if is_rename_target_filename:
                if current_file is not None:
                    raise UnidiffParseError('Target without source: %s' % line)
                # prefix with 'b/' to match expected git source format