code: public int argOffset(String name) {
          for (int i = 0; i < argNames.length; i++) {
              if (argNames[i].equals(name)) return i;
          }
          return -1;
      }
docs: Retrieve the offset of the given argument name in this signature's
  arguments. If the argument name is not in the argument list, returns -1.
  
  @param name the argument name to search for
  @return the offset at which the argument name was found or -1