anchor.diff:    ///
     /// If [mode] is provided as either [HtmlEscapeMode.attribute] or
     /// [HtmlEscapeMode.element], only the corresponding subset of HTML
  -  /// characters are escaped.
  +  /// characters is escaped.
     /// The default is to escape all HTML characters.
     const HtmlEscape([this.mode = HtmlEscapeMode.unknown]);
   
  
positive.code: ///
  /// Custom escape modes can be created using the [HtmlEscapeMode.HtmlEscapeMode]
  /// constructor.
  class HtmlEscapeMode {
    final String _name;
  
  
negative.code: 
  /// Converter which escapes characters with special meaning in HTML.
  ///
  /// The converter finds characters that are significant in the HTML source and
  /// replaces them with corresponding HTML entities.
  ///
  /// The characters that need escaping in HTML are:
  ///
  /// * `&` (ampersand) always needs to be escaped.
  /// * `<` (less than) and `>` (greater than) when inside an element.
  /// * `"` (quote) when inside a double-quoted attribute value.
  /// * `'` (apostrophe) when inside a single-quoted attribute value.
  ///       Apostrophe is escaped as `&#39;` instead of `&apos;` since
  