private SymbolicExpressionTreeGrammar(SymbolicExpressionTreeGrammar original, Cloner cloner)
   : base(original, cloner) {
   this.grammar = original.grammar;
 }
 private SymbolicExpressionTreeGrammar(SymbolicExpressionTreeGrammar original, Cloner cloner)
     : base(original, cloner)
 {
     this.grammar = original.grammar;
 }