Integration: DeepSource (#407)

* Refactor unnecessary `else` / `elif` when `if` block has a `return` statement

* Remove unused imports

* Use literal syntax to create data structure

* revert "remove unused import"

* Create .deepsource.toml

.deepsource.toml

@@ -0,0 +1,12 @@
+version = 1
+
+test_patterns = ["tests/**/test_*.py"]
+
+exclude_patterns = ["docs/**"]
+
+[[analyzers]]
+name = "python"
+enabled = true
+
+  [analyzers.meta]
+  runtime_version = "3.x.x"