[Typing][B-92] Add type annotations for python/paddle/batch.py

python/paddle/batch.py

@@ -12,10 +12,19 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from __future__ import annotations
+
+from typing import Callable, Generator, TypeVar
+
+_T = TypeVar('_T')
 __all__ = []
 
 
-def batch(reader, batch_size, drop_last=False):
+def batch(
+    reader: Callable[[], Generator[_T, None, None]],
+    batch_size: int,
+    drop_last: bool = False,
+) -> Callable[[], Generator[list[_T], None, None]]:
     """
     This operator creates a batched reader which combines the data from the
     input reader to batched data.