docstr: Test dtype_policy default value.
docstr_tok: ["Test","dtype_policy","default","value","."]
code: def test_dtype_policy_default(self):
      """Test dtype_policy default value."""
      policy = dtype_policy()
      self.assertEqual(policy.name, "float32")
  
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 5 for calling the DTypePolicyGlobalFunctionsTest obj's underlying member method code with example usage: obj.test_dtype_policy_default() without return types