ids__union
ids1 = ids__union(ids1, ids2);
ids1 = ids__union(ids1, ids2);
ids1 = ids__union(ids1, ids2);
ids1 = ids__union(ids1, ids2);
struct hashmap *ids__union(struct hashmap *ids1, struct hashmap *ids2);
ctx->ids = ids__union($1.ids, ctx->ids);
.ids = ids__union(ids1.ids, ids2.ids),