code: def use_backend(name):
      """Call fastmath functions with a specified backend."""
      if isinstance(name, Backend):
          name = name.value
  
      _assert_valid_backend_name(name)
      global override_backend
      prev_name_or_backend = override_backend
      override_backend = name
      # Run the decorated function in try-finally in case it throws, e.g. for tests.
      try:
          yield
      finally:
          override_backend = prev_name_or_backend
  
imports: import contextlib
  import enum
  import gin
  from trax.fastmath.jax import JAX_BACKEND
  from trax.fastmath.numpy import NUMPY_BACKEND
  from trax.fastmath.tf import TF_BACKEND
label_desc: Use image node_id 44 for calling a global function with example usage: use_backend(name) without return types