code: func prefixACLs(c context.Context, prefix string, in []*packageACL) []*packageACL {
  	root := rootKey(c)
  	for _, r := range legacyRoles {
  		in = append(in, &packageACL{
  			ID:     r + ":" + prefix,
  			Parent: root,
  		})
  	}
  	return in
  }
docs: // prefixACLs appends empty packageACL entities (with keys populated) to the
  // given slice and returns the new slice.
  //
  // The added entities have keys '<role>:<prefix>' where <role> goes over all
  // possible roles. Adds exactly len(legacyRoles) entities.