code: def test_on_train_step_end(self) -> None:
      with tempfile.TemporaryDirectory() as temp_dir:
          memory_snapshot = MemorySnapshot(
              output_dir=temp_dir,
          )
          memory_snapshot.memory_snapshot_profiler = Mock()
  
          mock_state, mock_unit = MagicMock(), MagicMock()
          memory_snapshot.on_train_step_end(mock_state, mock_unit)
  
          memory_snapshot.memory_snapshot_profiler.step.assert_called_once()
  
file_path: tnt/tests/framework/callbacks/test_memory_snapshot.py
imports: import tempfile
  import unittest
  from unittest.mock import MagicMock, Mock
  from torchtnt.framework.callbacks.memory_snapshot import MemorySnapshot
  from torchtnt.framework.state import EntryPoint
label_desc: Use image node_id 1 for calling the TestMemorySnapshot obj's underlying member method code with example usage: obj.test_on_train_step_end() without return types