If this line fails, then the time will not be set back.  This could cause the rest of the test suite to run slower.  It's probably worth wrapping this line in a `try/except/finally` block:

    try:
        return world.browser.is_element_not_present_by_css(css_selector, wait_time=wait_time)
    except:
        raise
    finally:
        world.browser.driver.implicitly_wait(world.IMPLICIT_WAIT)