Add return self to various methods to support chaining

[JonnyWong16]

Description

Add return self to most methods to support method chaining.

Type of change

Please delete options that are not relevant.

• [x] New feature (non-breaking change which adds functionality)
• [ ] This change requires a documentation update

Checklist:

• [x] My code follows the style guidelines of this project
• [x] 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