code: def insert(self, var, value, index=None):
          
          current = self.__get(var)
          if not isinstance(current, list):
              raise KeyError("%s: is not a list" % var)
          if index is None:
              current.append(value)
          else:
              current.insert(index, value)
          if self.auto_save:
              self.save()
docs: Insert at the index.
  
          If the index is not provided appends to the end of the list.