code: def phylotree(self):
          
          if not self._phylotree or self._dirty:
              try:
                  if ISPY3:
                      self._phylotree = PhyloTree(self.newick.encode(), self.rooted)
                  else:
                      self._phylotree = PhyloTree(self.newick, self.rooted)
              except ValueError:
                  logger.error('Couldn\'t convert to C++ PhyloTree -- are there bootstrap values?')
              self._dirty = False
          return self._phylotree
docs: Get the c++ PhyloTree object corresponding to this tree.
          :return: PhyloTree instance