code: def test_previous_backend(backend):
      if not ivy.backend_stack:
          assert ivy.previous_backend() is None
  
      ivy.set_backend(backend)
      stack_before_unset = []
      func_address_before_unset = id(ivy.sum)
      stack_before_unset.extend(ivy.backend_stack)
  
      previous_backend = ivy.previous_backend()
      stack_after_unset = ivy.backend_stack
      # check that the function id has changed as inverse=True.
      ivy.utils.assertions.check_equal(
          func_address_before_unset,
          id(ivy.sum),
          inverse=True,
          as_array=False,
      )
      ivy.utils.assertions.check_equal(
          previous_backend,
          importlib.import_module(_backend_dict[backend]),
          as_array=False,
      )
      ivy.utils.assertions.check_greater(
          len(stack_before_unset),
          len(stack_after_unset),
          as_array=False,
      )
  
      # checking a previously set backend is still set
      ivy.set_backend(backend)
      ivy.set_backend("numpy")
      ivy.previous_backend()
      ivy.utils.assertions.check_equal(
          ivy.current_backend_str(), backend, as_array=False
      )
  
file_path: ivy/ivy_tests/test_ivy/test_misc/test_backend_utils/test_backend_handler.py
imports: from packaging import version
  import pytest
  import importlib
  import types
  import numpy
  import ivy
  from ivy.utils.backend.handler import _backend_dict
  from ivy_tests.test_ivy.helpers.available_frameworks import _available_frameworks
label_desc: Use image node_id 6 for calling a global function with example usage: test_previous_backend(backend) without return types