pySim/utils: define 'Hexstr' using NewType
This means Hexstr is no longer an alias for 'str', but a distinct
new type, a sub-class of 'str'.
Change-Id: Ifb787670ed0e149ae6fcd0e6c0626ddc68880068
diff --git a/pySim/utils.py b/pySim/utils.py
index c6362fa..b534580 100644
--- a/pySim/utils.py
+++ b/pySim/utils.py
@@ -7,7 +7,7 @@
import abc
import string
from io import BytesIO
-from typing import Optional, List, Dict, Any, Tuple
+from typing import Optional, List, Dict, Any, Tuple, NewType
# Copyright (C) 2009-2010 Sylvain Munaut <tnt@246tNt.com>
# Copyright (C) 2021 Harald Welte <laforge@osmocom.org>
@@ -27,7 +27,7 @@
#
# just to differentiate strings of hex nibbles from everything else
-Hexstr = str
+Hexstr = NewType('Hexstr', str)
def h2b(s: Hexstr) -> bytearray: