key_down(value, element=None)
Sends a key press only, without releasing it.
Should only be used with modifier keys (Control, Alt and Shift).
Args:
value: The modifier key to send. Values are defined in Keys class.
element: The element to send keys. If None, sends a key to current focused element.
Example, pressing ctrl+c:
ActionChains(driver).key_down(Keys.CONTROL).send_keys('c').key_up(Keys.CONTROL).perform()