ValueError occurred when building cascaded model with loaded sub-model
Hi, @tilakrayal 

I've tested on co-lab whether this problem can be reproduced with TensorFlow Nightly.
Then the error occurred on there, so i updated the description of this issue above 👆 

Thanks! @keisen,
By default Tensorflow v2.16 uses keras v3.0 which might be the reason for the error you are facing. As the work-around, Could you please try to install keras 2 where the code was executed without any issue/error. Kindly find the gist of it [here](https://colab.research.google.com/gist/tilakrayal/59285ac9a54836f764cc271f6f4ebde4/untitled1778.ipynb).

```python
!pip install -U tf_keras # Keras 2
import os
os.environ["TF_USE_LEGACY_KERAS"] = "1"
```

Thank you! @tilakrayal , Thank you for the quick response!

> As the work-around, Could you please try to install keras 2 where the code was executed without any issue/error.

Unfortunately, I can't choose the way you suggested. so i hope it will be fixed asap...
Please let me know another way or when you expect it to be done.

Thanks! @keisen,
As mentioned above, it is the workaround for the temporary usage. Since this request is specific to Keras 3.0, could you please close here and open a new issue in Keras repo https://github.com/keras-team/keras/issues for quick resolution. 
Thank you!
 @tilakrayal 

Yeah, I thought you might say so. So I did it already lol
https://github.com/keras-team/keras/issues/19374

Thank you for your help.
Regards! Are you satisfied with the resolution of your issue?
<a href="https://docs.google.com/forms/d/e/1FAIpQLSfaP12TRhd9xSxjXZjcZFNXPGk4kc1-qMdv3gc6bEP90vY1ew/viewform?entry.85265664=Yes&entry.2137816233=https://github.com/tensorflow/tensorflow/issues/64393">Yes</a>
<a href="https://docs.google.com/forms/d/e/1FAIpQLSfaP12TRhd9xSxjXZjcZFNXPGk4kc1-qMdv3gc6bEP90vY1ew/viewform?entry.85265664=No&entry.2137816233=https://github.com/tensorflow/tensorflow/issues/64393">No</a>

### Issue type

Bug

### Have you reproduced the bug with TensorFlow Nightly?

YES

### Source

binary

### TensorFlow version

tf 2.16.1

### Custom code

No

### OS platform and distribution

Ubuntu on Windows 10 WSL2

### Mobile device

_No response_

### Python version

3.10.13

### Bazel version

_No response_

### GCC/compiler version

_No response_

### CUDA/cuDNN version

_No response_

### GPU model and memory

_No response_

### Current behavior?

Hi, tensorflow team!

I'm facing a error when build cascaded model with sub-model loaded from a file.
It's okay if the sub-model is NOT loaded from file, just created on memory.
This behavior appeared form tf 2.16+. Until tf 2.15-, it didn't exist definitely.

Please improve this issue or let me know how to work around....

Thanks!

### Standalone code to reproduce the issue

```shell
https://gist.github.com/keisen/4703d6508a950ff6a35d84da73e335b8
```


### Relevant log output

```shell
ValueError                                Traceback (most recent call last)
<ipython-input-7-2fefc420998f> in <cell line: 1>()
----> 1 model = create_cascaded_model(loaded_child_model)
      2 model.summary()

<ipython-input-5-e10dc8c731da> in create_cascaded_model(_child_model)
      3     x = tf.keras.layers.Conv2D(3, 3, padding='same', activation='relu', name='conv_1')(inputs)
      4     x = _child_model(x)
----> 5     x = tf.keras.layers.Dense(1, name='dense_2')(x)
      6     return tf.keras.models.Model(inputs=inputs, outputs=x)

/usr/local/lib/python3.10/dist-packages/keras/src/utils/traceback_utils.py in error_handler(*args, **kwargs)
    120             # To get the full stack trace, call:
    121             # `keras.config.disable_traceback_filtering()`
--> 122             raise e.with_traceback(filtered_tb) from None
    123         finally:
    124             del filtered_tb

/usr/local/lib/python3.10/dist-packages/keras/src/backend/common/variables.py in standardize_dtype(dtype)
    431 
    432     if dtype not in ALLOWED_DTYPES:
--> 433         raise ValueError(f"Invalid dtype: {dtype}")
    434     return dtype
    435 

ValueError: Invalid dtype: tuple
```
