style: format code with Black, isort and Rustfmt

This commit fixes the style issues introduced in 9413c64 according to the output
from Black, isort and Rustfmt.

Details: #13

Author: deepsource-autofix[bot]

prod_test.py

@@ -1,5 +1,7 @@
 # This should be at the top.
-from __future__ import print_function
+from __future__ import (
+    print_function,
+)
 
 import math
 import os