tensorflow: Report: AutoGraph could not transform, module 'gast' has no attribute 'Index'

System information

• source: https://www.tensorflow.org/tutorials/text/transformer
• OS Platform: ArchLinux 5.8.14 x86_64
• TensorFlow installed from (source or binary): binary : https://www.archlinux.org/packages/community/x86_64/tensorflow-cuda/
• TensorFlow version (use command below): 2.3.1 -2
• Python version: 3.8.6
• Bazel version (if compiling from source):
• GCC/Compiler version (if compiling from source):
• CUDA/cuDNN version: 11.1.0 -2 https://www.archlinux.org/packages/community/x86_64/cuda/
• GPU model and memory: GeForce GTX 1660 SUPER computeCapability: 7.5, 22 deviceMemorySize: 5.80GiB

Describe the current behavior

WARNING:tensorflow:AutoGraph could not transform 
<function train_step at 0x7f15c0790ee0> and will run it as-is.
Please report this to the TensorFlow team. When filing the bug, 
set the verbosity to 10 (on Linux, `export AUTOGRAPH_VERBOSITY=10`) and attach the full output.
Cause: module 'gast' has no attribute 'Index'

Describe the expected behavior

Standalone code to reproduce the issue python transformer.py

Other info / logs Include any logs or source code that would be helpful to transformer.zip