Gantt Chart tooltip Label Language

[Ashish]

Hi there

I am using the Gantt Chart and I am aware that we cant customize tooltip content for Gantt chart yet. I am trying to implement localization by using

 google.charts.load('current', { 'packages': ['gantt'],'language':'fr' });

But still, Labels like "Duration:" in the tooltip is still in English. How can I change them according to the language specified? If Not,  Is there any way I can change it before rendering, etc.

Thank you