code: private boolean validFormat(final String s) {
          String[] args = ARGS_REGEX.split(s);
          if (noItems(args)) return false;
          if (args.length < 3) return false;
  
          // Check for the presence of a function name
          String name = args[0];
          if (name.isEmpty()) return false;
          if (!validFunction(name)) return false;
  
          // Check for the presence of a return type
          String returntype = args[args.length - 1];
          if (returntype.isEmpty()) return false;
          if (!validReturnType(returntype)) return false;
  
          // Check for zero or more arguments
          String arglist = args[1];
          if (arglist.isEmpty()) return true;
  
          // Split parameters on comma
          String[] argsplit = arglist.split(",");
          for (final String arg : argsplit) {
              if (!validParameter(arg)) return false;
          }
          return true;
      }
docs: Returns {@code true} if the string {@code s} adheres to the signature
  format, {@code false} otherwise.
  
  @param s String
  @return boolean