Return associatinos in id2gos format

def read_associations(assoc_fn, anno_type='id2gos', **kws):
    """Return associatinos in id2gos format"""
    # kws get_objanno: taxids hdr_only prt allow_missing_symbol
    obj = get_objanno(assoc_fn, anno_type, **kws)
    # kws get_id2gos: ev_include ev_exclude keep_ND keep_NOT b_geneid2gos go2geneids
    return obj.get_id2gos(**kws)