# Wrapper for `mongoc_collection_save()`.
	#
	# This function shall save a document into the collection.
	# If the document has an `_id` field it will be updated.
	# Otherwise it will be inserted.
	#
	# You can retrieve a generated `_id` from `sys.last_mongoc_id`.
	fun save(document: NativeBSON): Bool import set_mongoc_error, set_mongoc_last_id `{
		bson_oid_t oid;
		if(!bson_has_field(document, "_id")) {
			bson_oid_init (&oid, NULL);
			BSON_APPEND_OID (document, "_id", &oid);
			NativeMongoCollection_set_mongoc_last_id(self, &oid);
		}
		bson_error_t error;
		if(!mongoc_collection_save(self, document, NULL, &error)) {
			NativeMongoCollection_set_mongoc_error(self, &error);
			return false;
		}
		return true;
	`}