code: def list(self, toa=None, show_history=False):
          
          if not toa:
              toa = time.mktime(datetime.datetime.now().timetuple())
  
          query = {
              "$query": {
                  "master_id": self.master_id,
                  "processed": show_history,
                  "toa" : {"$lte" : toa}
              },
              "$orderby": {
                  "toa": 1
              }
          }
  
          revisions = yield self.revisions.find(query)
  
          raise Return(revisions)
docs: Return all revisions for this stack
  
          :param int toa: The time of action as a UTC timestamp
          :param bool show_history: Whether to show historical revisions