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()
      precision.backward(tensor, model, "positional-arg", keyword="arg")
      precision.scaler.scale.assert_called_once_with(tensor)
      tensor.backward.assert_called_once_with(
          "positional-arg", keyword="arg"
      )
  
file_path: pytorch-lightning/tests/tests_fabric/plugins/precision/test_fsdp.py
imports: from unittest.mock import Mock
  import pytest
  import torch
  from lightning.fabric.plugins import FSDPPrecision
  from lightning.fabric.plugins.precision.utils import _DtypeContextManager
  from tests_fabric.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