add __all__ to meta

Author: bckohan

enum_properties/meta.py

@@ -12,6 +12,15 @@
 from enum import Enum, EnumMeta
 
 
+__all__ = [
+    'EnumProperties',
+    'EnumPropertiesMeta',
+    'SymmetricMixin',
+    'p',
+    's'
+]
+
+
 def _do_casenorm(text):
     """Normalize unicode text to be case agnostic."""
     return unicodedata.normalize('NFKD', text.casefold())