Returns the $ value of the first meta element with
    the @property that matches @prop_name (or None).

def find_val_for_first_bf_l_meta(d, prop_name):
    """Returns the $ value of the first meta element with
    the @property that matches @prop_name (or None).
    """
    m_list = d.get('meta')
    if not m_list:
        return None
    if not isinstance(m_list, list):
        m_list = [m_list]
    for m_el in m_list:
        if m_el.get('@property') == prop_name:
            return extract_meta(m_el)
    return None