fix: added type annotations to fix mypy failure in CI (#28933)

openedx/core/djangoapps/content/learning_sequences/api/processors/enrollment_track_partition_groups.py

@@ -1,6 +1,7 @@
 # lint-amnesty, pylint: disable=missing-module-docstring
 import logging
 from datetime import datetime
+from typing import Dict
 
 from opaque_keys.edx.keys import CourseKey
 from openedx.core import types
@@ -12,6 +13,7 @@ from xmodule.partitions.partitions import (
     ENROLLMENT_TRACK_PARTITION_ID,
 )
 from xmodule.partitions.partitions_service import get_user_partition_groups
+from xmodule.partitions.partitions import Group
 
 from .base import OutlineProcessor
 
@@ -28,10 +30,10 @@ class EnrollmentTrackPartitionGroupsOutlineProcessor(OutlineProcessor):
     """
     def __init__(self, course_key: CourseKey, user: types.User, at_time: datetime):
         super().__init__(course_key, user, at_time)
-        self.enrollment_track_groups = {}
+        self.enrollment_track_groups: Dict[str, Group] = {}
         self.user_group = None
 
-    def load_data(self, full_course_outline):
+    def load_data(self, full_course_outline) -> None:
         """
         Pull track groups for this course and which group the user is in.
         """