code: protected Element elementBeforeImpl(String name) {
          String prefix = getPrefixFromQualifiedName(name);
          String namespaceURI = this.xmlNode.lookupNamespaceURI(prefix);
          return elementBeforeImpl(name, namespaceURI);
      }
docs: Add a named XML element to the document as a sibling element
  that precedes the position of this builder node.
  
  When adding an element to a namespaced document, the new node will be
  assigned a namespace matching it's qualified name prefix (if any) or
  the document's default namespace. NOTE: If the element has a prefix that
  does not match any known namespaces, the element will be created
  without any namespace.
  
  @param name
  the name of the XML element.
  
  @throws IllegalStateException
  if you attempt to add a sibling element to a node where there are already
  one or more siblings that are text nodes.