code: public static CellFormulaExpression copyOf(CellFormulaExpression formula) {
          if (formula == null) { return null; }
          CellFormulaExpression copy = new CellFormulaExpression();
  
          copy.formulaStr = formula.formulaStr().intern();
          copy.formulaValues = formula.formulaValues().intern();
          copy.formulaPtgStr = formula.formulaPtgStr().intern();
          copy.ptgStr = formula.ptgStr().intern();
          copy.iptg = formula.iptg();
          copy.rootFormulaId = formula.rootFormulaId;    
          copy.ptgs(formula.ptgs);    
          copy.formulaPtg(formula.formulaPtg());
  
          return copy;
      }
docs: Does copy of provided instance.