code: def test_fsdp_precision_backward():
      precision = FSDPPrecision(precision="16-mixed")
      precision.scaler = Mock()
      precision.scaler.scale = Mock(side_effect=(lambda x: x))
      tensor = Mock()
      model = Mock(trainer=Mock(callbacks=[], profiler=MagicMock()))
      precision.pre_backward(tensor, model)
      precision.backward(
          tensor, model, None, "positional-arg", keyword="arg"
      )
      precision.scaler.scale.assert_called_once_with(tensor)
      model.backward.assert_called_once_with(
          tensor, "positional-arg", keyword="arg"
      )
  
file_path: pytorch-lightning/tests/tests_pytorch/plugins/precision/test_fsdp.py
imports: from unittest.mock import ANY, MagicMock, Mock
  import pytest
  import torch
  from lightning.fabric.plugins.precision.utils import _DtypeContextManager
  from lightning.pytorch.plugins.precision.fsdp import FSDPPrecision
  from tests_pytorch.helpers.runif import RunIf
label_desc: Use image node_id 5 for calling a global function with example usage: test_fsdp_precision_backward() without return types