code: func NewLayerProvidersFromStores(lss map[string]layer.Store) map[string]PushLayerProvider {
  	plps := make(map[string]PushLayerProvider)
  	for os, ls := range lss {
  		plps[os] = &storeLayerProvider{ls: ls}
  	}
  	return plps
  }
docs: // NewLayerProvidersFromStores returns layer providers backed by
  // an instance of LayerStore. Only getting layers as gzipped
  // tars is supported.