Making Envs module pass MyPy checks (#2048)

* Fix configs.py None MyPy error

* Use img_tensor instead of img in utils.py

* Add type assertion in factory.py

* Resolve merge conflict

* Uncomment envs moodule for mypy checks in pyproject.toml

---------

Signed-off-by: Adil Zouitine <adilzouitinegm@gmail.com>
Co-authored-by: Adil Zouitine <adilzouitinegm@gmail.com>

.pre-commit-config.yaml

@@ -86,12 +86,12 @@ repos:
 
   # TODO(Steven): Uncomment when ready to use
   ##### Static Analysis & Typing #####
-  # - repo: https://github.com/pre-commit/mirrors-mypy
-  #   rev: v1.16.0
-  #   hooks:
-  #     - id: mypy
-  #       args: [--config-file=pyproject.toml]
-  #       exclude: ^(examples|benchmarks|tests)/
+  - repo: https://github.com/pre-commit/mirrors-mypy
+    rev: v1.16.0
+    hooks:
+      - id: mypy
+        args: [--config-file=pyproject.toml]
+        exclude: ^(examples|benchmarks|tests)/
 
   ##### Docstring Checks #####
   # - repo: https://github.com/akaihola/darglint2