code: def remember(self, chain=-1, trace_index=None):
          
          if trace_index is None:
              trace_index = randint(self._cur_trace_index)
  
          for variable in self._variables_to_tally:
              if isinstance(variable, Stochastic):
                  try:
                      variable.value = self.trace(
                          variable.__name__,
                          chain=chain)[trace_index]
                  except:
                      cls, inst, tb = sys.exc_info()
                      warnings.warn(
                          'Unable to remember value of variable %s. Original error: \n\n%s: %s' %
                          (variable, cls.__name__, inst.message))
docs: remember(chain=-1, trace_index = randint(trace length to date))
  
          Sets the value of all tracing variables to a value recorded in
          their traces.