Return the value of the item 'key'.

def get_item_key(self, item):
        """Return the value of the item 'key'."""
        try:
            ret = item[item['key']]
        except KeyError:
            logger.error("No 'key' available in {}".format(item))
        if isinstance(ret, list):
            return ret[0]
        else:
            return ret