Function fetch_layer 

pub(crate) async fn fetch_layer<'a>(
    proxy: &'a ImageProxy,
    img: &OpenedImage,
    manifest: &ImageManifest,
    layer: &'a Descriptor,
    progress: Option<&'a Sender<Option<LayerProgress>>>,
    layer_info: Option<&Vec<ConvertedLayerInfo>>,
    transport_src: Transport,
) -> Result<(Box<dyn AsyncBufRead + Send + Unpin>, impl Future<Output = Result<()>> + 'a, MediaType)>

A wrapper for [get_blob] which fetches a layer and decompresses it.