code: def previousElementSibling(self):
          
          ret = libxml2mod.xmlPreviousElementSibling(self._o)
          if ret is None:return None
          __tmp = xmlNode(_obj=ret)
          return __tmp
docs: Finds the first closest previous sibling of the node which
            is an element node. Note the handling of entities
            references is different than in the W3C DOM element
            traversal spec since we don't have back reference from
             entities content to entities references.