Expires header

Hi! I have been using litespeed cache for a while and it is working so well. My performance in Pingdom has improved a lot, but the expires header issue is still there. When I check the .htaccess file, I find the following <IfModule mod_expires.c> and I assume it is something similar with mod_expires that creates expires header. How can I check if the expires header is working on my site? If not, what should I do or should I just ignore this warning from pingdom?

Pingdom result: https://tools.pingdom.com/#5a23d3a383400000

Thank you for reading!

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