I made attempt to create a trait shared between lossy and lossless variants of Repository, but this has following flaws:

• Interface over lossy variant works nice as we can refer to member; I tried Cow<> but now dealing with fact Paragraph::get() may fail become a problem (unwrap() is plain wrong).
• Use Cow<> is going to work for some cases, but may be a problem for some others, especially if wrapped in Option<>
• For optional fields use of .ok() turns potential errors of late parsing into None, I have doubts if it's acceptable.

Problems with lossless structure:

• Paragraphs are copied out of Deb822, there's not reference to them
• If lossless::Repositories store Deb822, I can only create lossless::Repository from these paragraphs, there's not way to return reference to them (that's different than in lossy variant).

Maybe I'm heading in wrong direction (no modifications/setting taken into account yet), as this route gives me identical API of both variants, but with problems. Maybe the role of lossless variant should be to produce out lossy variant and accept one to perform modifications.

Can we discuss pros and cons?