Translating a string from plugin.

Everything is working fine with theme translation using pll__ or pll_e
but when I try to add this to a plugin, in my example it’s slider plugin with names included. It doesn’t show up in strings translation. Is there any way to work around this? As far as I’m concerned it looks like it’s not possible or I am doing something wrong.

https://wordpress.org/plugins/polylang/