def _modify_dataset(
        self,
        anonymizer: Anonymizer,
        pseudonym: str,
        ds: Dataset,
) -> None:
    """Optionally pseudonymize an incoming dataset with the given pseudonym
    and add the trial ID and name to the DICOM header if specified."""
    if pseudonym:
        # All dates get pseudonymized, but we want to retain the study date.
        study_date = ds.StudyDate

        anonymizer.anonymize(ds)

        ds.StudyDate = study_date

        ds.PatientID = pseudonym
        ds.PatientName = pseudonym

    trial_protocol_id = (self.transfer_task.job.trial_protocol_id,)
    trial_protocol_name = self.transfer_task.job.trial_protocol_name

    if trial_protocol_id:
        ds.ClinicalTrialProtocolID = trial_protocol_id

    if trial_protocol_name:
        ds.ClinicalTrialProtocolName = trial_protocol_name

    if pseudonym and trial_protocol_id:
        session_id = f"{ds.StudyDate}-{ds.StudyTime}"
        ds.PatientComments = f"Project:{trial_protocol_id} Subject:{pseudonym} Session:{pseudonym}_{session_id}"