Fixed pylint issues (pytest requirement)

.github/workflows/pylint.yml

@@ -18,7 +18,7 @@ jobs:
       run: |
         python -m pip install --upgrade pip
         pip install pylint
-        pip install -r requirements.txt -r requirements-tf.txt
+        pip install -r requirements.txt -r requirements-tf.txt -r requirements-dev.txt
     - name: Analysing the code with pylint
       run: |
         pylint $(git ls-files '*.py')