DRY version of similar string processing
<p>What would be a more efficient way to do the following:</p>

<pre><code>directors = get_element_or_none(title_node, 'Director')
producers = get_element_or_none(title_node, 'Producer')
writers = get_element_or_none(title_node, 'Writer')

if directors:
    directors = [director.strip() for director in directors.split(',')]
if producers:
    producers = [producer.strip() for producer in producers.split(',')]
if writers:
    writers = [writer.strip() for writer in writers.split(',')]
</code></pre>
