code: def test_init(self) -> None:
      empty = MapData()
      self.assertTrue(empty.map_df.empty)
  
      with self.assertRaisesRegex(
          ValueError, "map_key_infos may be `None` iff"
      ):
          MapData(df=self.df, map_key_infos=None)
  
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 3 for calling the MapDataTest obj's underlying member method code with example usage: obj.test_init() without return types