code: def setUp(self) -> None:
      self.non_exponential_ndcg = NDCGMetric(
          world_size=WORLD_SIZE,
          my_rank=0,
          batch_size=BATCH_SIZE,
          tasks=[DefaultTaskInfo],
          # pyre-ignore
          exponential_gain=False,  # exponential_gain is one of the kwargs
          # pyre-ignore
          session_key=SESSION_KEY,  # session_key is one of the kwargs
      )
  
      self.exponential_ndcg = NDCGMetric(
          world_size=WORLD_SIZE,
          my_rank=0,
          batch_size=BATCH_SIZE,
          tasks=[DefaultTaskInfo],
          # pyre-ignore
          exponential_gain=True,  # exponential_gain is one of the kwargs
          # pyre-ignore
          session_key=SESSION_KEY,  # session_key is one of the kwargs
      )
  
file_path: torchrec/torchrec/metrics/tests/test_ndcg.py
imports: import unittest
  from typing import Dict
  import torch
  from torchrec.metrics.metrics_config import DefaultTaskInfo
  from torchrec.metrics.ndcg import NDCGMetric, SESSION_KEY
label_desc: Use image node_id 1 for calling the NDCGMetricValueTest obj's underlying member method code with example usage: obj.setUp() without return types