def check_not_indexed_objects(object_map: list, xref_seq: list):
    """List objects that are not indexed by any xref structure."""
    ret = []
    indexed = set()
    for xref in xref_seq:
        errors = []
        for o in xref:
            if o['o_num'] <= 0:
                continue
            if 'env_num' in o:
                k = ('EMB', o['o_num'], o['env_num'], o['o_pos'])
            else:
                k = ('DIR', o['o_num'], o['o_gen'], o['abs_pos'])
            indexed.add(k)
    ind_objs = [x for x in object_map if x[2] == 'IND_OBJ']
    for x in ind_objs:
        if type(x[0]) == int:
            o = ('DIR', x[3]['o_num'], x[3]['o_gen'], x[0])
        elif type(x[0]) == float:
            o = ('EMB', x[3]['o_num'], x[3]['env_num'], x[1][2])
        else:
            continue
        if o not in indexed:
            ret.append(o)
    return ret
List objects that are not indexed by any xref structure.
pdfsyntax/filestruct.py