The tokens _struct_ref_seq.seq_align_beg, _struct_ref_seq.seq_align_end, and _struct_ref_seq_dif.seq_num are listed in the parent-child list (in the first 2 cases) but not in the _item.name-category-mandatory_code list (in all 3 cases) of _entity_poly_seq.num, making it hard to infer their types.