Fix errors found in mypy and add mypy to CI (#1185)

Author: shueja

.github/workflows/choreolib.yml

@@ -241,6 +241,23 @@ jobs:
         with:
           name: Python
           path: ./choreolib/py/dist
+  lint-python:
+    name: "Lint Python"
+    runs-on: ubuntu-24.04
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+          persist-credentials: false
+          token: ${{secrets.GITHUB_TOKEN}}
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: 3.12
+
+      - run: pip3 install mypy wpilib
+
+      - run: mypy --pretty --show-column-numbers choreolib/py
 
   pypi-publish:
     name: Upload release to PyPI

choreolib/py/choreo/__init__.py

@@ -8,6 +8,7 @@
     SwerveSample,
     SwerveTrajectory,
     load_event_marker,
+    marker_is_not_none,
 )
 from choreo.util.traj_schema_version import (
     TRAJ_SCHEMA_VERSION as generated_TRAJ_SCHEMA_VERSION,
@@ -48,18 +49,18 @@ def load_differential_trajectory_string(
             float(sample["omega"]),
             float(sample["al"]),
             float(sample["ar"]),
-            [float(x) for x in sample["fl"]],
-            [float(y) for y in sample["fr"]],
+            float(sample["fl"]),
+            float(sample["fr"]),
         )
         for sample in data["trajectory"]["samples"]
     ]
     splits = [int(split) for split in data["trajectory"]["splits"]]
     # Add 0 as the first split index
     if len(splits) == 0 or splits[0] != 0:
         splits.insert(0, 0)
-    events = list(
+    events = list[EventMarker](
         filter(
-            lambda marker: marker is not None,
+            marker_is_not_none,
             [load_event_marker(event) for event in data["events"]],
         )
     )
@@ -122,9 +123,9 @@ def load_swerve_trajectory_string(trajectory_json_string: str) -> SwerveTrajecto
     # Add 0 as the first split index
     if len(splits) == 0 or splits[0] != 0:
         splits.insert(0, 0)
-    events = list(
+    events = list[EventMarker](
         filter(
-            lambda marker: marker is not None,
+            marker_is_not_none,
             [load_event_marker(event) for event in data["events"]],
         )
     )