@Override public void fillAssignedKeys(Set<String> keys){
  TreeSet<String> subKeys=new TreeSet<>();
  for (  ExprKraken expr : _exprs) {
    subKeys.clear();
    expr.fillAssignedKeys(subKeys);
    keys.addAll(subKeys);
  }
}

@ Override public void fillAssignedKeys ( Set < String > keys ) { TreeSet < String > subKeys = new TreeSet < > ( ) ; for ( ExprKraken expr : _exprs ) { subKeys . clear ( ) ; expr . fillAssignedKeys ( subKeys ) ; keys . addAll ( subKeys ) ; } }
returns all the keys assigned statically , e . g . by param or literal .
