code: def set_doc_data_lic(self, doc, res):
          
          if not self.doc_data_lics_set:
              self.doc_data_lics_set = True
              # TODO: what is this split?
              res_parts = res.split('/')
              if len(res_parts) != 0:
                  identifier = res_parts[-1]
                  doc.data_license = document.License.from_identifier(identifier)
              else:
                  raise SPDXValueError('Document::License')
          else:
              raise CardinalityError('Document::License')
docs: Set the document data license.
          Raise exceptions:
          - SPDXValueError if malformed value,
          - CardinalityError if already defined.