Develop black format fix (#1998)

* fixed the format

* changed the circleci config

.circleci/config.yml

             mkdir test-reports
             pytest --cov=mlagents --cov-report xml --junitxml=test-reports/junit.xml -p no:warnings
             python-codacy-coverage -r coverage.xml
+
+      - run:
+          name: Check Code Style for ml-agents and gym_unity using black
+          command: |
+            . venv/bin/activate
             black --check ml-agents
             black --check ml-agents-envs
             black --check gym-unity

gym-unity/gym_unity/envs/unity_env.py

             visual_obs = info.visual_observations
             if isinstance(visual_obs, list):
                 visual_obs = np.array(visual_obs)
-            self.visual_obs = self._preprocess_single(
-                visual_obs[0][0, :, :, :]
-            )
+            self.visual_obs = self._preprocess_single(visual_obs[0][0, :, :, :])
             default_observation = self.visual_obs
         else:
             default_observation = info.vector_observations[0, :]