Align the ordering of class methods

[dmdunla]

We should decide on the order of the class methods. Unless there is standard ordering that we should follow, below is a suggestion.

Suggestion:

• __init__
• from_* class methods
• methods in alphabetical order
• dunder (__<foo>__) methods in alphabetical order

Currently the method orderings are different across the classes.

[jeremy-myers]

I think this ordering is intuitive. I can take this on after a second opinion.