docs: def get_uefi_boot_string(self, mac):
          """Get uefi iscsi boot string for the host
  
          :returns: iscsi boot string for the system
          :raises: IloError, on an error from iLO.
          """
          boot_sources = self.boot_sources
          if not boot_sources:
              msg = ('Boot sources are not found')
              LOG.debug(msg)
              raise exception.IloError(msg)
  
          for boot_source in boot_sources:
              if (mac.upper() in boot_source['UEFIDevicePath'] and
                      'iSCSI' in boot_source['UEFIDevicePath']):
                  return boot_source['StructuredBootString']
          else:
              msg = ('MAC provided "%s" is Invalid' % mac)
              raise exception.IloInvalidInputError(msg)