def METHOD_NAME(self) -> List[UpstreamConfigFilename]:
    pattern = re.compile(rf'{self.upstream_prefix}\d+_\d+.json')
    with ConfigFileManager.CFM_LOCK:
        filenames = get_files_with_prefix(
            self.dirname,
            self.upstream_prefix
        )
        return sorted(
            map(
                UpstreamConfigFilename.from_filename,
                filter(pattern.search, filenames)
            )
        )