mypy fixed types

shared/data_store/put.py

@@ -1,4 +1,5 @@
 """Definition of put function."""
+
 from __future__ import annotations
 
 import logging
@@ -16,8 +17,8 @@ def put(
     """Put buffer in bucket in MinIO and return MD5 checksum as object name."""
     assert isinstance(client, Minio)
     assert isinstance(buffer, BytesIO)
-    bucket_name = os.getenv('MINIO_BUCKET_NAME', default=None)
-    assert isinstance(bucket_name, str)
+    bucket_name = os.getenv('MINIO_BUCKET_NAME', default='')
+    assert len(bucket_name) > 0
     # get md5 of image
     checksum = md5(buffer.getbuffer()).hexdigest()
     # prepare for saving