Error with DICOM series and PET normalization


I’m trying to calculate the radiomics features with pyradiomics in 3Dslicer. However, when i’m trying to normalize the DICOM series with PETDICOMExtension, i get a warning, which shows the following error: series does not have radiopharmaceutical code sequence.
Is there a problem with my DICOM series?
Can i calculate the radiomics features without normalizing the DICOM series?

Thanks for your help!!