code: func (stub *MockStub) GetStateByPartialCompositeKey(objectType string, attributes []string) (StateQueryIteratorInterface, error) {
  	partialCompositeKey, err := stub.CreateCompositeKey(objectType, attributes)
  	if err != nil {
  		return nil, err
  	}
  	return NewMockStateRangeQueryIterator(stub, partialCompositeKey, partialCompositeKey+string(maxUnicodeRuneValue)), nil
  }
docs: //GetStateByPartialCompositeKey function can be invoked by a chaincode to query the
  //state based on a given partial composite key. This function returns an
  //iterator which can be used to iterate over all composite keys whose prefix
  //matches the given partial composite key. This function should be used only for
  //a partial composite key. For a full composite key, an iter with empty response
  //would be returned.