Karatsuba type annotation (#9800)

* Replacing the generator with numpy vector operations from lu_decomposition.

* Revert "Replacing the generator with numpy vector operations from lu_decomposition."

This reverts commit ad217c6.

* Added type annotation.

Author: quant12345

Diff for: maths/karatsuba.py

@@ -1,7 +1,7 @@
 """ Multiply two numbers using Karatsuba algorithm """
 
 
-def karatsuba(a, b):
+def karatsuba(a: int, b: int) -> int:
     """
     >>> karatsuba(15463, 23489) == 15463 * 23489
     True