eslint: no return assign

So I'm having a problem with a no return assign but my script seems good can someone help me with it?

The script is:

(function() {
    'use strict';
    let root = document.querySelector(":root");
    root.style.setProperty("--tv-color-pane-background", "#00开发者_开发技巧0");

    setTimeout(() => document.querySelector("html.theme-dark .tv-floating-toolbar").style.backgroundColor = "black", 1000);
})();

on the settimeout line It's giving me this error:enter image description here