docstr: Test set_dtype_policy with an invalid input.
docstr_tok: ["Test","set_dtype_policy","with","an","invalid","input","."]
code: def test_set_dtype_policy_invalid(self):
      """Test set_dtype_policy with an invalid input."""
      with self.assertRaisesRegex(
          ValueError, "Invalid `policy` argument"
      ):
          set_dtype_policy(12345)
  
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 4 for calling the DTypePolicyGlobalFunctionsTest obj's underlying member method code with example usage: obj.test_set_dtype_policy_invalid() without return types