docstr: Test set_dtype_policy with a valid DTypePolicy object.
docstr_tok: ["Test","set_dtype_policy","with","a","valid","DTypePolicy","object","."]
code: def test_set_dtype_policy_valid_policy(self):
      """Test set_dtype_policy with a valid DTypePolicy object."""
      policy_obj = DTypePolicy("mixed_float16")
      set_dtype_policy(policy_obj)
      policy = dtype_policy()
      self.assertEqual(policy.name, "mixed_float16")
  
imports: from keras.mixed_precision import DTypePolicy
  from keras.mixed_precision import dtype_policy
  from keras.mixed_precision import set_dtype_policy
  from keras.testing import test_case
label_desc: Use image node_id 3 for calling the DTypePolicyGlobalFunctionsTest obj's underlying member method code with example usage: obj.test_set_dtype_policy_valid_policy() without return types