def update(self, dicomset):
if not isinstance(dicomset, DicomFileSet):<EOL><INDENT>raise ValueError('<STR_LIT>')<EOL><DEDENT>self.items = list(set(self.items).update(dicomset))<EOL>
Update this set with the union of itself and dicomset.

        Parameters
        ----------
        dicomset: DicomFileSet