How to read UDA data by latest OCC7.8.0

Hello, I ues the sample given in the "New feature - STEP Import | User Defined Attributes", code as:
Handle(TDocStd_Document) aDoc = new TDocStd_Document("MDTV-XCAF");
Standard_CString filename = "E:\WorkSpace\metadataFile.stp";
STEPCAFControl_Reader reader;
reader.ReadFile(filename);
if(reader.Transfer(aDoc)){
std::cout << "Translate successful\n";
}else{
std::cout << "Translate failed\n";
}
Handle(XCAFDoc_ShapeTool) aShapeTool = XCAFDoc_DocumentTool::ShapeTool(aDoc->Main());
NCollection_IndexedDataMap<TCollection_AsciiString, Handle(TDataStd_NamedData)> aNameDataMap; // Container to keep label's entry and its metadata
for (TDF_ChildIterator anIter(aShapeTool->Label(), Standard_True); anIter.More(); anIter.Next())
{
const TDF_Label& aLabel = anIter.Value();
TCollection_AsciiString anEntry;
TDF_Tool::Entry(aLabel, anEntry);
Handle(TDataStd_NamedData) aNamedData = aShapeTool->GetNamedProperties(aLabel);
if (!aNamedData.IsNull())
{
aNameDataMap.Add(anEntry, aNamedData);
}
}

But it falied while using the transfer() function.
How to translate a stp file to document for parsing UDA data?
Any help is greatly appreciated. Thank you!