code: def load(self, config, dataset_type="train", *args, **kwargs):
      dataset = NumbersDataset(
          DATASET_LEN, data_item_key="input", always_one=True
      )
      dataset.dataset_name = self.dataset_name
      dataset.dataset_type = dataset_type
      return dataset
  
file_path: mmf/tests/data/user_dir/datasets/always_one.py
imports: from mmf.common.registry import registry
  from mmf.datasets.base_dataset_builder import BaseDatasetBuilder
  from tests.test_utils import NumbersDataset
label_desc: Use image node_id 4 for calling the AlwaysOneBuilder obj's underlying member method code with example usage: obj.load(config, dataset_type) and returns: dataset