style: enforcing mypy typing for connectors (#9824)

Co-authored-by: John Bodley <john.bodley@airbnb.com>

superset/utils/import_datasource.py

@@ -15,15 +15,22 @@
 # specific language governing permissions and limitations
 # under the License.
 import logging
+from typing import Callable, Optional
 
+from flask_appbuilder import Model
+from sqlalchemy.orm import Session
 from sqlalchemy.orm.session import make_transient
 
 logger = logging.getLogger(__name__)
 
 
 def import_datasource(
-    session, i_datasource, lookup_database, lookup_datasource, import_time
-):
+    session: Session,
+    i_datasource: Model,
+    lookup_database: Callable,
+    lookup_datasource: Callable,
+    import_time: Optional[int] = None,
+) -> int:
     """Imports the datasource from the object to the database.
 
      Metrics and columns and datasource will be overrided if exists.
@@ -75,7 +82,7 @@ def import_datasource(
     return datasource.id
 
 
-def import_simple_obj(session, i_obj, lookup_obj):
+def import_simple_obj(session: Session, i_obj: Model, lookup_obj: Callable) -> Model:
     make_transient(i_obj)
     i_obj.id = None
     i_obj.table = None