def _filter_col8(interval, keys=None):
    """
    Filter the content of last column in interval.

    Parameters
    ----------
    interval : pybedtools.Interval
        Interval.
    keys : list
        List of keys that should be kept in result.

    Returns
    -------
    string
        Filtered content of last column.

    """
    if keys is None:
        keys = ['gene_id', 'gene_name', 'transcript_id', 'transcript_name']
    return ' '.join(['{} "{}";'.format(key, value) for key, value in
                     sorted(interval.attrs.items()) if key in keys])