Meaning? "One of a kind. Top of the line. A real doggone keeper"

One of a kind. Top of the line. A real doggone keeper

This a phrase spoken by Walter to Chris in the movie "Get Out". YouTube link

I think I can understand the first two phrases...

"One of a kind, top of the line" means the best female among all other females.

Okay, but what does "A real doggone keeper" mean?

A girl can keep a boy? Control a boy? Attracting the mind of a boy? so that the boy will never betray her?

Is that what it means?

Doggone

attributive

Used to express feelings of annoyance, surprise, or pleasure. ‘now just a doggone minute’. - OLD

Given the context of "One of a kind. Top of the line", the feeling being expressed here is pleasure.

The word keeper is being used informally:

Keeper

informal

Someone with good qualities, who you can have a long relationship with. - Cambridge

A real doggone keeper means someone that has truly great qualities, someone who the speaker would like to have a long relationship with.