To verify the correctness, I started to press the keys after clicking on the input to see whether they are being clicked.
elem = driver.find_element_by_id("q")
elem.send_keys('t')
ActionChains(driver).key_down(Keys.LEFT_SHIFT).send_keys('ff').perform()
The code above will enter into the input tFF, that is, the left shift is clamped. But you should rewrite it to CTRL + t:
elem = driver.find_element_by_id("q")
elem.send_keys('t')
ActionChains(driver).key_down(Keys.LEFT_CONTROL).send_keys('t').perform()
And it does not work, even though it should be logical.