Instantiating query object

Constructor of the Query class has default anytype parameter named _source. To my knowledge there are four different ways to use it:

1. Instantiating an empty query – no parameter value should be specified:
   Query q = new Query();


2. Instantiating a query based on the AOT query:
   Query q = new Query(querystr(Alertsetup));


3. Instantiating a query as the copy of another query:
   Query q1 = new Query();
   Query q2 = new Query(q1);


4. Instantiating a query from the container with the packed query
   Query q1 = new Query();
   Query q2 = new Query(q1.pack());

Is there anything else that can be used as a source for constructing a query?