Let's implicitly fix a typo (#681)

(At least until Python 2.7 support is finally eliminated)

.github/workflows/ci.yml

@@ -17,9 +17,9 @@ jobs:
           - "3.9"
           - "3.10"
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v3
       - name: Set up Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
         with:
           python-version: ${{ matrix.python-version }}
       - name: Install ffmpeg
@@ -37,8 +37,9 @@ jobs:
   black:
     runs-on: ubuntu-20.04
     steps:
-      - uses: actions/checkout@v2
-      - uses: psf/black@21.12b0 # TODO: upgrade after dropping Python 2 support.
-        with:
-          src: ffmpeg  # TODO: also format `examples`.
-          version: 21.12b0
+      - uses: actions/checkout@v3
+      - name: Black
+        run: |
+          # TODO: use standard `psf/black` action after dropping Python 2 support.
+          pip install black==21.12b0 click==8.0.2  # https://stackoverflow.com/questions/71673404
+          black ffmpeg --check --color --diff

ffmpeg/dag.py

@@ -74,7 +74,7 @@ class DagNode(object):
         """Provides information about all incoming edges that connect to this node.
 
         The edge map is a dictionary that maps an ``incoming_label`` to
-        ``(outgoing_node, outgoing_label)``.  Note that implicity, ``incoming_node`` is
+        ``(outgoing_node, outgoing_label)``.  Note that implicitly, ``incoming_node`` is
         ``self``.  See "Edges" section above.
         """
         raise NotImplementedError()