Fix mypy errors

Signed-off-by: Levko Kravets <[email protected]>

Author: kravets-levko

src/databricks/sqlalchemy/base.py

@@ -406,7 +406,7 @@ def get_table_comment(
 sqlalchemy_version_tag_pat = r"sqlalchemy/(\d+\.\d+\.\d+)"
 
 
-def add_sqla_tag_if_not_present(val: str):
+def add_sqla_tag_if_not_present(val: Optional[str] = None):
     if val is None or val == "":
         output = SQLALCHEMY_TAG
     elif re.search(sqlalchemy_version_tag_pat, val):