Code improvements using Numpy

[tosemml]

Overview

Refactorings to improve code

Description of Changes

Use np.cumsum to compute the cumulative sum, which is efficient and concise.

Screenshots

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code + updated documentation (if necessary)
• I have added tests to define the behavior of the feature(s) and verify it is working
• New + existing unit tests pass