@SuppressWarnings("unchecked")
    public Q on(Predicate... conditions) {
        queryMixin.addJoin(JoinType.JOIN, ExpressionUtils.as((Path) ref, target));
        queryMixin.on(conditions);
        return queryMixin.getSelf();
    }
{@code JoinBuilder} is a builder for join constraints

@author Mark Paluch

@param <Q>
@param <T>
querydsl-mongodb/src/main/java/com/querydsl/mongodb/document/JoinBuilder.java