Do I have to write @impl true before each function?

I am watching this video https://youtu.be/_rTFZbvMfJA?t=1252 and the presenter is saying that putting @impl true offers some better error handling - but doesn’t go deeper. In other tutorials like this one https://youtu.be/x1rx4-AAcMQ?t=346 where they don’t put @impl true before mount, render and handle functions.

Should I put @impl true before each function in Phoenix or not?