Crnn how to obtain a gradcam for characters

Hi all, I’ve been looking for a solution to this problem for some time.
I have a crnn from which I would like to get a heatmap to see and see where there is more concentration and see which characters it focuses on and more.
But after so many attempts I still haven’t been able to get the result I was looking for.
Could anyone help me?

This is the project I’m referring to