def METHOD_NAME(filename=version_info_filename):
    """ Get the version info from the installed distribution.
        :param filename: Base filename of the version info resource.
        :return: The version info as a mapping of fields. If the
            distribution is not available, the mapping is empty.
        The version info is stored as a metadata file in the
        distribution.
        """
    version_info = {
            'release_date': "UNKNOWN",
            'version': "UNKNOWN",
            'maintainer': "UNKNOWN",
            }
    try:
        distribution = pkg_resources.get_distribution(distribution_name)
    except pkg_resources.DistributionNotFound:
        distribution = None
    if distribution is not None:
        if distribution.has_metadata(version_info_filename):
            content = distribution.get_metadata(version_info_filename)
            version_info = json.loads(content)
    return version_info