code: function childContentWrapper(element) {
      var wrapper = undefined;
      for (var c = element.firstChild; c; c = c.nextSibling) {
        var type = c.nodeType;
        wrapper = (type === 1)  // Element Node
            ? (wrapper ? element : c)
            : (type === 3)  // Text Node
            ? (notWs.test(c.nodeValue) ? element : wrapper)
            : wrapper;
      }
      return wrapper === element ? undefined : wrapper;
    }
docs: Given an element, if it contains only one child element and any text nodes
  it contains contain only space characters, return the sole child element.
  Otherwise returns undefined.
  <p>
  This is meant to return the CODE element in {@code <pre><code ...>} when
  there is a single child element that contains all the non-space textual
  content, but not to return anything where there are multiple child elements
  as in {@code <pre><code>...</code><code>...</code></pre>} or when there
  is textual content.