> omit_fields implies omitting [all the] tiddler.fields

Well, I suppose that wouldn't be a problem if default argument values could be non-primitives: `omit_fields=[]` - that would make it clear what is meant is "omit *these* fields". But since the default value is `None` rather than `False`, I guess that's enough of a hint?

> Perhaps `omit_attr` or `omit_attributes` as that is more aligned with the Python word for what is being omitted

But we *don't* want to suggest this is any arbitrary attribute - we're specifically talking about (standard) tiddler fields here (thus `for field in self.tiddler_fields`).

So the naming confusion seems to come largely from your end: To me, "fields" means the standard tiddler fields (title, text, modifier etc.) - whereas "custom fields" means the "fields" field/attribute. If that is not correct, we should rename some variables in the Tiddler model and here.