docs: public Selector intern(InternTable table)
    {
      // This implementation is inherited by Identifier and Literal which have no children,
      // but is overridden in Operator, which does.
      Selector me = (Selector) table.get(this);
      if (me != null)
      {
        me.incRefCount();
        return me;
      }
      else
      {
        uniqueId = table.getNextUniqueId();
        refCount++;
        table.put(this, this);
        return this;
      }
    }