code: def check_session(self, key, *, session=None):
          
          self.append({
              "Verb": "check-session",
              "Key": key,
              "Session": extract_attr(session, keys=["ID"])
          })
          return self
docs: Fails the transaction if Key is not currently locked by Session
  
          Parameters:
              key (str): Key to check
              session (ObjectID): Session ID