code: public static String returnValue(CtBehavior method) throws NotFoundException {
  
          String returnValue = "";
          if (methodReturnsValue(method)) {
              returnValue = " returns: \" + $_ + \".";
          }
          return returnValue;
      }
docs: Create a javassist source snippet which either is empty (for anything
  which does not return a value) or a explanatory text around the $_
  javassist return value variable.
  
  @param method
  descriptor of method
  @return source snippet
  @throws NotFoundException