def get_key_value(key, article_raw):
    """
    Searches for an entry in article_raw (which is a list of dicts) that
    has the 'key'. Then it returns the value associated to that key. 
    If the key is not found, return None.
    """ 
    sel = list(filter(lambda d: d['key']==key, article_raw))
    if len(sel)==0:
        return None
    return sel[0]['value']