def METHOD_NAME():
    """Check that the ``CRDS_PATH`` environment variable is set. This
    will be the location to which CRDS reference files are downloaded.
    If the env variable is not set, default to use ``$HOME/crds_cache/``
    Returns
    -------
    crds_path : str
        Full path to the location of the CRDS reference files
    """
    crds_path = os.environ.get('CRDS_PATH')
    if crds_path is None:
        reffile_dir = '{}/crds_cache'.format(os.environ.get('HOME'))
        os.environ["CRDS_PATH"] = reffile_dir
        ensure_dir_exists(reffile_dir)
        print('CRDS_PATH environment variable not set. Setting to {}'.format(reffile_dir))
        return reffile_dir
    else:
        return crds_path