Assert provided content is not contained within an element found by ``id``.

def element_not_contains(self, element_id, value):
    """
    Assert provided content is not contained within an element found by ``id``.
    """
    elem = world.browser.find_elements_by_xpath(str(
        'id("{id}")[contains(., "{value}")]'.format(
            id=element_id, value=value)))
    assert not elem, \
        "Expected element not to contain the given text."