code: func (stub *MockStub) DelState(key string) error {
  	mockLogger.Debug("MockStub", stub.Name, "Deleting", key, stub.State[key])
  	delete(stub.State, key)
  
  	for elem := stub.Keys.Front(); elem != nil; elem = elem.Next() {
  		if strings.Compare(key, elem.Value.(string)) == 0 {
  			stub.Keys.Remove(elem)
  		}
  	}
  
  	return nil
  }
docs: // DelState removes the specified `key` and its value from the ledger.