style: format code with Black, ISort and Rustfmt

This commit fixes the style issues introduced in abdc075 according to the output
from Black, ISort and Rustfmt.

Details: #13

Author: deepsource-dev-autofix[bot]

prod_test.py

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