code: def addSibling(self, elem):
          
          if elem is None: elem__o = None
          else: elem__o = elem._o
          ret = libxml2mod.xmlAddSibling(self._o, elem__o)
          if ret is None:raise treeError('xmlAddSibling() failed')
          __tmp = xmlNode(_obj=ret)
          return __tmp
docs: Add a new element @elem to the list of siblings of @cur
            merging adjacent TEXT nodes (@elem may be freed) If the new
            element was already inserted in a document it is first
             unlinked from its existing context.