Merge pull request #635 from bashtage/fix-mypy

MAINT: Fix small mypy issue

Author: bashtage

linearmodels/iv/absorbing.py

@@ -69,7 +69,7 @@
 
 
 class Hasher:
-    def __init__(self):
+    def __init__(self) -> None:
         self._hasher: hashlib._Hash | xxh64
         if HAVE_XXHASH:
             self._hasher = xxh64()