js_command = "return document.documentElement.outerHTML;".
By this code I'm able to get the source code, but not the rendered one. I can do
js_command = "return document;" (as I would do in console), but than I will get
<selenium.webdriver.firefox.webelement.FirefoxWebElement (session="5a784804-f623-3041-9840-03f13ce83f53", element="585b43a1-f3b2-1e4a-b348-4ddaf2944550")> object that has the HTML but it's not possible to get it out of it.