module 'keras.api._v2.keras.experimental' has no attribute 'PeepholeLSTMCell'

I tried to install tensorflow_federated in google colab. I used

pip install --quiet tensorflow-federated-nightly
import tensorflow-federated as tff

and it worked. but now when I try to import it get this error:

AttributeError: module 'keras.api._v2.keras.experimental' has no attribute 'PeepholeLSTMCell'

I don't know why I get this error, because I didn't have any problem before.

I also used the following code to install tensorflow-federated:

pip install --upgrade tensorflow-federated-nightly 

but I get the same error.

How do I fix it?

My versions are:

tensorflow 2.8.0, keras 2.8.0, tensorflow-federated-nightly 0.19.0.dev20220218