def get_tuple(from_var):
    """Convert tuples, strings and None into tuple."""
    if type(from_var) is tuple:
        return from_var
    elif type(from_var) is str:
        return (from_var,)
    elif from_var is None:
        return ()
    else:
        raise TypeError('Value should be either tuple, string or None, ' +
                        'received: ' + type(from_var).__name__)