code: def setUp(self) -> None:
      self.df = pd.DataFrame(
          [
              {
                  "arm_name": "0_0",
                  "epoch": 0,
                  "mean": 2.0,
                  "sem": 0.2,
                  "trial_index": 1,
                  "metric_name": "a",
              },
              {
                  "arm_name": "0_0",
                  "epoch": 0,
                  "mean": 1.8,
                  "sem": 0.3,
                  "trial_index": 1,
                  "metric_name": "b",
              },
              {
                  "arm_name": "0_1",
                  "epoch": 0,
                  "mean": 4.0,
                  "sem": 0.6,
                  "trial_index": 1,
                  "metric_name": "a",
              },
              {
                  "arm_name": "0_1",
                  "epoch": 0,
                  "mean": 3.7,
                  "sem": 0.5,
                  "trial_index": 1,
                  "metric_name": "b",
              },
              {
                  "arm_name": "0_1",
                  "epoch": 1,
                  "mean": 0.5,
                  "sem": None,
                  "trial_index": 1,
                  "metric_name": "a",
              },
              {
                  "arm_name": "0_1",
                  "epoch": 1,
                  "mean": 3.0,
                  "sem": None,
                  "trial_index": 1,
                  "metric_name": "b",
              },
          ]
      )
  
      self.map_key_infos = [
          MapKeyInfo(
              key="epoch",
              default_value=0,
          )
      ]
  
      self.mmd = MapData(df=self.df, map_key_infos=self.map_key_infos)
  
file_path: Ax/ax/core/tests/test_map_data.py
imports: import pandas
  from ax.core.data import Data
  from ax.core.map_data import MapData, MapKeyInfo
  from ax.utils.common.testutils import TestCase
label_desc: Use image node_id 1 for calling the MapDataTest obj's underlying member method code with example usage: obj.setUp() without return types