code: public SmartHandle dropLast(String newName, Class<?> type) {
          return new SmartHandle(signature.appendArg(newName, type), MethodHandles.dropArguments(handle, signature.argOffset(newName), type));
      }
docs: Drop an argument from the handle at the end, returning a new
  SmartHandle.
  
  @param newName name of the argument
  @param type type of the argument
  @return a new SmartHandle with the additional argument