code: def test_backends_installed():
      """
      This test will fail if some of backends are not installed or can't be imported
      Other tests will just work and only test installed backends.
      """
      from . import parse_backends_to_test
  
      backends_to_test = parse_backends_to_test()
      errors = []
      for backend_type in AbstractBackend.__subclasses__():
          if backend_type.framework_name not in backends_to_test:
              continue
          try:
              # instantiate
              backend_type()
          except Exception as e:
              errors.append((backend_type.framework_name, e))
      assert len(errors) == 0, errors
  
imports: import sys
  import unittest
  from doctest import testmod
  from typing import Dict, List, Optional
  import numpy
  import pytest
  from parameterized import parameterized, parameterized_class
  import einops
  import einops.layers
  import einops.parsing
  from einops._backends import AbstractBackend
  from einops.einops import rearrange, parse_shape, _optimize_transformation
  from .None import collect_test_backends, is_backend_tested
label_desc: Use image node_id 2 for calling a global function with example usage: test_backends_installed() without return types