code: private void addPattern(MethodSpec.Builder method, String pattern) {
      // Parse the pattern and populate the method body with instructions to format the date.
      for (Node node : DATETIME_PARSER.parse(pattern)) {
        if (node instanceof Text) {
          method.addStatement("b.append($S)", ((Text)node).text());
        } else if (node instanceof Field) {
          Field field = (Field)node;
          method.addStatement("formatField(d, '$L', $L, b)", field.ch(), field.width());
        }
      }
    }
docs: Add a named date-time pattern, adding statements to the formatting and indexing methods.
  Returns true if the pattern corresponds to a date; false if a time.