_escape(string) {
    var escaped = {
      "'": '&apos;',
      '"': '&quot;',
      '&': '&amp;',
      '>': '&gt;',
      '<': '&lt;'
    };

    return string.replace(/(['"&><])/g, (string, char) => {
      return escaped[char];
    });
  }
Returns an escaped string for use within XML.

@param   {string} string The string to escape
@returns {string} The escaped string