How to use the pyperf._metadata._common_metadata function in pyperf

def _display_common_metadata(metadatas, lines):
    if len(metadatas) < 2:
        return

    for metadata in metadatas:
        # don't display name as metadata, it's already displayed
        metadata.pop('name', None)

    common_metadata = _common_metadata(metadatas)
    if common_metadata:
        format_title('Common metadata', lines=lines)
        empty_line(lines)

        format_metadata(common_metadata, lines=lines)

    for key in common_metadata:
        for metadata in metadatas:
            metadata.pop(key, None)

def get_metadata(self):
        benchs_metadata = [bench._get_common_metadata()
                           for bench in self._benchmarks]
        return _common_metadata(benchs_metadata)

def _get_common_metadata(self):
        if self._common_metadata is None:
            runs_metadata = [run._metadata for run in self._runs]
            self._common_metadata = _common_metadata(runs_metadata)
        return self._common_metadata