'Duplicates the source.'

def _duplicate_item(self, parent_usage_key, source_usage_key, display_name=None):

    data = {'parent_locator': unicode(parent_usage_key), 'duplicate_source_locator': unicode(source_usage_key)}
    if (display_name is not None):
        data['display_name'] = display_name
    resp = self.client.ajax_post(reverse('contentstore.views.xblock_handler'), json.dumps(data))
    return self.response_usage_key(resp)
