good first issuehelp wanted
描述
TensorFlow 2.0 was released. We should consider upgrading our TF dependency to 2.0.
However, since this is large major version up, we still don't know how much source code needs to be rewritten for the upgrade.
Fortunately, there's a script tf_upgrade_v2.py to upgrade to TF 2.0. First, we should try this script and estimate how the upgrade is difficult.