def dump_header(iterable, allow_token=True):
    if isinstance(iterable, dict):
        items = []
        for key, value in iterable.iteritems():
            if value is None:
                items.append(key)
            else:
                items.append('%s=%s' % (
                    key,
                    quote_header_value(value, allow_token=allow_token)
                ))
    else:
        items = [quote_header_value(x, allow_token=allow_token)
                 for x in iterable]
    return ', '.join(items)
Dump an HTTP header again.  This is the reversal of
dataset/ETHPy150Open IanLewis/kay/kay/lib/werkzeug/http.py/dump_header