code: function sh_highlightElement(element, language) {
    sh_addClass(element, 'sh_sourceCode');
    var originalTags = [];
    var inputString = sh_extractTags(element, originalTags);
    var highlightTags = sh_highlightString(inputString, language);
    var tags = sh_mergeTags(originalTags, highlightTags);
    var documentFragment = sh_insertTags(tags, inputString);
    while (element.hasChildNodes()) {
      element.removeChild(element.firstChild);
    }
    element.appendChild(documentFragment);
  }
docs: Highlights an element containing source code.  Upon completion of this function,
  the element will have been placed in the "sh_sourceCode" class.
  @param  element  a DOM <pre> element containing the source code to be highlighted
  @param  language  a language definition object