'Simulates pressing the left mouse button on the element specified by `locator`.
The element is pressed without releasing the mouse button.
Key attributes for arbitrary elements are `id` and `name`. See
`introduction` for details about locating elements.
See also the more specific keywords `Mouse Down On Image` and
`Mouse Down On Link`.'

@keyword
def mouse_down(self, locator):

    self.info(("Simulating    Mouse    Down    on    element    '%s'" % locator))
    element = self.find_element(locator, required=False)
    if (element is None):
        raise AssertionError(('ERROR:    Element    %s    not    found.' % locator))
    action = ActionChains(self.browser)
    action.click_and_hold(element).perform()
