code: public Signature insertArg(String beforeName, String name, Class<?> type) {
          return insertArgs(argOffset(beforeName), new String[]{name}, new Class<?>[]{type});
      }
docs: Insert an argument (name + type) into the signature before the argument
  with the given name.
  
  @param beforeName the name of the argument before 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