Refactor cast function in utils.py

[Dr-Blank]

Description

ref: #1302 (comment)

• less indentation, more readable code
• early return

Type of change

Please delete options that are not relevant.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated the docstring for new or existing methods
• I have added tests when applicable