Update to support 3.9 and black for compatibility.

Author: FragmentedPacket

.github/workflows/ci.yml

@@ -13,8 +13,6 @@ jobs:
         uses: "actions/checkout@v2"
       - name: "Setup environment"
         uses: "networktocode/gh-action-setup-poetry-environment@v1"
-        with:
-          python-version: "3.9.7"
       - name: "Linting: black"
         run: "poetry run invoke black"
   bandit:

diffsync/helpers.py

@@ -85,7 +85,8 @@ def calculate_diffs(self) -> Diff:
 
         for obj_type in intersection(self.dst_diffsync.top_level, self.src_diffsync.top_level):
             diff_elements = self.diff_object_list(
-                src=self.src_diffsync.get_all(obj_type), dst=self.dst_diffsync.get_all(obj_type),
+                src=self.src_diffsync.get_all(obj_type),
+                dst=self.dst_diffsync.get_all(obj_type),
             )
 
             for diff_element in diff_elements:
@@ -220,7 +221,10 @@ def diff_object_pair(
         return diff_element
 
     def diff_child_objects(
-        self, diff_element: DiffElement, src_obj: Optional["DiffSyncModel"], dst_obj: Optional["DiffSyncModel"],
+        self,
+        diff_element: DiffElement,
+        src_obj: Optional["DiffSyncModel"],
+        dst_obj: Optional["DiffSyncModel"],
     ):
         """For all children of the given DiffSyncModel pair, diff recursively, adding diffs to the given diff_element.