AttributeError: 'google.protobuf.pyext._message.RepeatedCompositeCo' object has no attribute 'append'

I had same error with tensorflow (version 2.2.0-dev20200128) and fixed it by upgrading protobuf (As explained in this issue):

pip install -U protobuf==3.8.0

Or if your using Notebook (like Google Colab notebook) try this:

!pip install -U protobuf==3.8.0

If it was running fine until yesterday and you did not change anything, then check for two things- Th TF version, if it has changed bc recently they set 'default' TF version to 1.15.rc from 1.14.

If that is same then save this file and close all the colab windows even your chrome or whatever browser you are using then open again and try running the file.

EDIT: As I said above it must be because of the TF version. So revert back to the one that you used when the model was working. As you mentioned in your comments below it was working on version ‘dev20191010’, so rolling back to it will fix your issue.

Try opening 'New Python 3 notebook' from file and write code there,that solved my problem.