code: def encryption_details(self):
          
          event_type = self.findtext("event_type")
          if event_type != "encryption":
              raise AttributeError(
                  'PREMIS events of type "{}" have no encryption'
                  " details".format(event_type)
              )
          parsed_encryption_event_detail = self.parsed_event_detail
          encryption_program = _get_event_detail_attr(
              "program", parsed_encryption_event_detail
          )
          encryption_program_version = _get_event_detail_attr(
              "version", parsed_encryption_event_detail
          )
          encryption_key = _get_event_detail_attr("key", parsed_encryption_event_detail)
          return encryption_program, encryption_program_version, encryption_key
docs: Return as a 3-tuple, this PREMIS encryption event's program,
          version, and key used to perform the encryption.