@Override
public Stream<PluginProtos.CodeGeneratorResponse.File> generate(PluginProtos.CodeGeneratorRequest request)
        throws GeneratorException {
    // create a map from proto types to java types
    this.protoTypeMap = ProtoTypeMap.of(request.getProtoFileList());

    return request.getProtoFileList().stream()
            .filter(file -> request.getFileToGenerateList().contains(file.getName()))
            .map(this::handleProtoFile)
            .flatMap(Function.identity());
}