code: def tally(self, chain):
          
  
          value = self._getfunc()
  
          try:
              self._trace[chain][self._index[chain]] = value.copy()
          except AttributeError:
              self._trace[chain][self._index[chain]] = value
          self._index[chain] += 1
docs: Store the object's current value to a chain.
  
          :Parameters:
          chain : integer
            Chain index.