protected Document createQuery(@Nullable Predicate predicate) {
        if (predicate != null) {
            return (Document) serializer.handle(predicate);
        } else {
            return new Document();
        }
    }
Define a constraint for an embedded object

@param collection collection
@param target target
@return builder
querydsl-mongodb/src/main/java/com/querydsl/mongodb/document/AbstractMongodbQuery.java