anchor.diff:      return self.traversal.toString()
     def __getitem__(self,index):
       if type(index) is int:
  -      self.traversal = self.traversal.range(indices,indices+1)
  +      self.traversal = self.traversal.range(index,index+1)
       elif type(index) is slice:
           self.traversal = self.traversal.range(index.start,index.stop)
       else:
  
positive.code:     return self.traversal.toString()
    def __getitem__(self,index):
      if type(index) is int:
        self.traversal = self.traversal.range(indices,indices+1)
      elif type(index) is slice:
          self.traversal = self.traversal.range(index.start,index.stop)
      else:
  
negative.code:     return self.traversalString;
    def __getitem__(self,index):
      if type(index) is int:
        return self.range(index,index+1)
      elif type(index) is slice:
        return self.range(index.start,index.stop)
      else:
  