optional dependency

tests/flake8_project/pyproject.toml

@@ -9,3 +9,8 @@ authors = [
     { name = "Author Name", email = "author.name@example.com" },
 ]
 description = "A description of what the package is for."
+
+[project.optional-dependencies]
+CODE_QUALITY = [
+    "flake8",
+]