code: def unpatch_tensorflow(precision="float32"):
      """
      ``unpatch_tensorflow`` is used to unpatch optimized tensorflow classes to original ones.
  
      Meanwhile, set ``precision`` as global dtype policy.
  
      :param precision: str, specify the compute and variable dtypes, select from ``'float32'``
                        and ``'mixed_bfloat16'``. Once ``'float32'`` is set, both compute and
                        variable dtypes will be float32. When ``'mixed_bfloat16'`` is set,
                        the compute dtype is bfloat16 and the variable dtype is float32.
                        Default to be ``'float32'``.
      """
      mapping_tf = _get_patch_map()
  
      for mapping_iter in mapping_tf:
          setattr(mapping_iter[0], mapping_iter[1], mapping_iter[3])
  
      # Set the global dtype policy
      invalidInputError(
          precision in ["float32", "mixed_bfloat16"],
          "The parameter should be one of ['float32', 'mixed_bfloat16'] ",
          f"but got {precision}.",
      )
      from tensorflow.keras import mixed_precision
  
      mixed_precision.set_global_policy(precision)
  
imports: from importlib.util import find_spec
  from bigdl.nano.utils.common import invalidInputError
label_desc: Use image node_id 3 for calling a global function with example usage: unpatch_tensorflow(precision) without return types