def is_tag(obj):
    """Determines if `obj` is a tuple of two strings.

    Examples:

    >>> is_tag(('hello', 'yes'))
    True
    >>> is_tag(('hi', 22))
    False

    """
    try:
        return (
            isinstance(obj, tuple)
            and len(obj) == 2
            and all((isinstance(x, str) or x == None) for x in obj)
        )
    except:
        return False