def METHOD_NAME(obj, typestr_or_type):
    """is_type(obj, typestr_or_type) verifies if obj is of a certain type. It
    can take strings or actual python types for the second argument, i.e.
    'tuple'<->TupleType. 'all' matches all types.
    TODO: Should be extended for choosing more than one type."""
    if typestr_or_type == "all":
        return True
    if type(typestr_or_type) == type:
        test_type = typestr_or_type
    else:
        test_type = typestr2type.get(typestr_or_type, False)
    if test_type:
        return isinstance(obj, test_type)
    return False