code: public Signature insertArg(int index, String name, Class<?> type) {
          return insertArgs(index, new String[]{name}, new Class<?>[]{type});
      }
docs: Insert an argument (name + type) into the signature.
  
  @param index the index at which to insert
  @param name  the name of the new argument
  @param type  the type of the new argument
  @return a new signature with the added arguments