How to enable bfloat16 PyTorch/XLA on Google Colab

In PyTorch/XLA implementation, an environment vatiable XLA_USE_BF16 exists.
Regrettably It cannot see the TF_LOG on Google Colab.
(If some one know, how to set TF_LOG enable, please notice me.)
Is there any way to enable bfloat16 for Pytorch/XLA on Google Colab?

Ref.

try %env XLA_USE_BF16=1