remove cast, throw error if not SeaResultSet

Signed-off-by: varun-edachali-dbx <varun.edachali@databricks.com>

Author: varun-edachali-dbx

src/databricks/sql/backend/sea/backend.py

@@ -1,7 +1,7 @@
 import logging
 import time
 import re
-from typing import Any, Dict, Tuple, List, Optional, Union, TYPE_CHECKING, Set, cast
+from typing import Any, Dict, Tuple, List, Optional, Union, TYPE_CHECKING, Set
 
 from databricks.sql.backend.sea.models.base import ResultManifest
 from databricks.sql.backend.sea.utils.constants import (
@@ -718,11 +718,15 @@ def get_tables(
         )
         assert result is not None, "execute_command returned None in synchronous mode"
 
+        from databricks.sql.result_set import SeaResultSet
+
+        assert isinstance(
+            result, SeaResultSet
+        ), "execute_command returned a non-SeaResultSet"
+
         # Apply client-side filtering by table_types
         from databricks.sql.backend.sea.utils.filters import ResultSetFilter
-        from databricks.sql.result_set import SeaResultSet
 
-        result = cast(SeaResultSet, result)
         result = ResultSetFilter.filter_tables_by_type(result, table_types)
 
         return result

tests/unit/test_sea_backend.py

@@ -729,7 +729,10 @@ def test_get_schemas(self, sea_client, sea_session_id, mock_cursor):
     def test_get_tables(self, sea_client, sea_session_id, mock_cursor):
         """Test the get_tables method with various parameter combinations."""
         # Mock the execute_command method
-        mock_result_set = Mock()
+        from databricks.sql.result_set import SeaResultSet
+
+        mock_result_set = Mock(spec=SeaResultSet)
+
         with patch.object(
             sea_client, "execute_command", return_value=mock_result_set
         ) as mock_execute: