def _get_element_attr_or_none(document, selector, attribute):
element = document.cssselect(selector)<EOL>if element:<EOL><INDENT>return element[<NUM_LIT:0>].get(attribute)<EOL><DEDENT>return None<EOL>
Using a CSS selector, get the element and return the given attribute value, or None if no element.

Args:
    document (HTMLElement) - HTMLElement document
    selector (str) - CSS selector
    attribute (str) - The attribute to get from the element