def dump_header(iterable, allow_token=True):
    """Dump an HTTP header again.  This is the reversal of
    :func:`parse_list_header`, :func:`parse_set_header` and
    :func:`parse_dict_header`.  This also quotes strings that include an
    equals sign unless you pass it as dict of key, value pairs.

    >>> dump_header({'foo': 'bar baz'})
    'foo="bar baz"'
    >>> dump_header(('foo', 'bar baz'))
    'foo, "bar baz"'

    :param iterable: the iterable or dict of values to quote.
    :param allow_token: if set to `False` tokens as values are disallowed.
                        See :func:`quote_header_value` for more details.
    """
    if isinstance(iterable, dict):
        items = []
        for key, value in iteritems(iterable):
            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)