stronger typing in resultSet behaviour

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

Author: varun-edachali-dbx

src/databricks/sql/result_set.py

@@ -101,12 +101,12 @@ def fetchall(self) -> List[Row]:
         pass
 
     @abstractmethod
-    def fetchmany_arrow(self, size: int) -> Any:
+    def fetchmany_arrow(self, size: int) -> "pyarrow.Table":
         """Fetch the next set of rows as an Arrow table."""
         pass
 
     @abstractmethod
-    def fetchall_arrow(self) -> Any:
+    def fetchall_arrow(self) -> "pyarrow.Table":
         """Fetch all remaining rows as an Arrow table."""
         pass
 
@@ -251,7 +251,7 @@ def _convert_arrow_table(self, table):
         res = df.to_numpy(na_value=None, dtype="object")
         return [ResultRow(*v) for v in res]
 
-    def merge_columnar(self, result1, result2):
+    def merge_columnar(self, result1, result2) -> "ColumnTable":
         """
         Function to merge / combining the columnar results into a single result
         :param result1: