code: def update_fw(self, nids, fw_type, fw_ver, fw_path=None):
          
          fw_bin = None
          if fw_path:
              fw_bin = load_fw(fw_path)
              if not fw_bin:
                  return
          self.ota.make_update(nids, fw_type, fw_ver, fw_bin)
docs: Update firwmare of all node_ids in nids.