What is the variable used for TOC caption?

[sachin-suresh-rapyuta]

I am trying multiple ways to use different toc captions based on PDF language.

Also, seems that below ifconfig doesnt work inside if-builder.

.. ifconfig:: language == 'en'

   .. toctree::
      :maxdepth: 2
      :caption: User Guide

.. ifconfig:: language == 'ja'

   .. toctree::
      :maxdepth: 2
      :caption: ユーザーガイド