code: def transactions(self, dt=None):
          
          if dt is None:
              # flatten the by-day transactions
              return [
                  txn
                  for by_day in itervalues(self._processed_transactions)
                  for txn in by_day
              ]
  
          return self._processed_transactions.get(dt, [])
docs: Retrieve the dict-form of all of the transactions in a given bar or
          for the whole simulation.
  
          Parameters
          ----------
          dt : pd.Timestamp or None, optional
              The particular datetime to look up transactions for. If not passed,
              or None is explicitly passed, all of the transactions will be
              returned.
  
          Returns
          -------
          transactions : list[dict]
              The transaction information.