[Minor] Loading interventions as non-static method

[frankaging]

Description

This is a basic support of loading in intervention weights with a non-static method.

Testing Done

[Manual testing]

Checklist:

• [x] My PR title strictly follows the format: [Your Priority] Your Title
• [x] I have attached the testing log above
• [x] I provide enough comments to my code
• [x] I have changed documentations
• [ ] I have added tests for my changes