- introduce n_processes to change the number of processes in the pool

.github/workflows/pytest.yml

@@ -11,9 +11,9 @@ jobs:
         os: [ubuntu-20.04, windows-2019, macOS-11]
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Set up Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v4
+        uses: actions/setup-python@v5
         with:
           python-version: ${{ matrix.python-version }}
       - name: Install