Although the debian repository format describes that a stanza should begin with 'Package' it also states that clients may accept other formats.

Each stanza shall begin with a "Package" field. Clients may also accept files where this is not the case. (see https://wiki.debian.org/DebianRepository/Format)

However, the _parse_repository fails if the first line is not Package.

In my opinion, the parses should only fail when there no "Package" key in the block of lines. Although unconventional, below should be parsed correctly.

Architecture: amd64
Description: HelloWorld
Maintainer: HelloWorld
Package: helloworld
Priority: optional
Section: devel
Version: 0.0.1
...etc