code: def addPrevSibling(self, elem):
          
          if elem is None: elem__o = None
          else: elem__o = elem._o
          ret = libxml2mod.xmlAddPrevSibling(self._o, elem__o)
          if ret is None:raise treeError('xmlAddPrevSibling() failed')
          __tmp = xmlNode(_obj=ret)
          return __tmp
docs: Add a new node @elem as the previous sibling of @cur
            merging adjacent TEXT nodes (@elem may be freed) If the new
            node was already inserted in a document it is first
            unlinked from its existing context. If the new node is
            ATTRIBUTE, it is added into properties instead of children.
            If there is an attribute with equal name, it is first
             destroyed.