docs: static CharInput asCharInput(final CharSequence chars) {
      checkNotNull(chars);
      return new CharInput() {
        int index = 0;
  
        @Override
        public int read() {
          if (index < chars.length()) {
            return chars.charAt(index++);
          } else {
            return -1;
          }
        }
  
        @Override
        public void close() {
          index = chars.length();
        }
      };
    }