code: def get_oplog_cursor(self, timestamp=None):
          
          query = {"op": {"$ne": "n"}}
          if timestamp is None:
              cursor = self.oplog.find(query, cursor_type=CursorType.TAILABLE_AWAIT)
          else:
              query["ts"] = {"$gte": timestamp}
              cursor = self.oplog.find(
                  query, cursor_type=CursorType.TAILABLE_AWAIT, oplog_replay=True
              )
          return cursor
docs: Get a cursor to the oplog after the given timestamp, excluding
          no-op entries.
  
          If no timestamp is specified, returns a cursor to the entire oplog.