code: def check_and_correct(self, cfg):
      # check the num_classes in model, train_dataset and val_dataset config
      model_cfg = cfg.model_cfg
      train_dataset_cfg = cfg.train_dataset_cfg
      val_dataset_cfg = cfg.val_dataset_cfg
      assert (
          train_dataset_cfg != {}
      ), "No train_dataset specified in the configuration file."
      if train_dataset_cfg["type"] != "Dataset":
          return
      if val_dataset_cfg != {}:
          assert (
              val_dataset_cfg["type"] == "Dataset"
          ), "The type of train_dataset and val_dataset must be the same"
          assert (
              "num_classes" in val_dataset_cfg
          ), "No num_classes specified in train_dataset config."
      assert (
          "num_classes" in train_dataset_cfg
      ), "No num_classes specified in train_dataset config."
  
      value_set = set()
      value_name = "num_classes"
      if value_name in model_cfg:
          value_set.add(model_cfg[value_name])
      if value_name in train_dataset_cfg:
          value_set.add(train_dataset_cfg[value_name])
      if value_name in val_dataset_cfg:
          value_set.add(val_dataset_cfg[value_name])
  
      if len(value_set) > 1:
          raise ValueError(
              "`num_classes` is not consistent: {}. Please set it "
              "consistently in model, train_dataset and val_dataset config".format(
                  value_set
              )
          )
      if len(value_set) == 1 and value_name not in model_cfg:
          logger.warning(
              "Add the `num_classes` in train_dataset and val_dataset "
              "config to model config. We suggest you manually set `num_classes` in model config."
          )
          model_cfg[value_name] = value_set.pop()
          cfg.dic["model"] = model_cfg
  
imports: import copy
  from paddleseg.utils import logger
  from paddleseg.utils import utils
label_desc: Use image node_id 1 for calling the DefaultSyncNumClassesRule obj's underlying member method code with example usage: obj.check_and_correct(cfg) without return types