Could not get layers list for image with specific tag

[andreishtilman]

How do I get the layers for the image with tag. I believe it should be as
./registry.py -r http://my-registry:5000 -i my_ubuntu:18.04 --layers

But this gives me:
Image: my_ubuntu:18.04
no tags!
Is it a bug? or I do something wrong?

Of course it works with no tag:
./registry.py -r http://my-registry:5000 -i my_ubuntu --layers

Image: my_ubuntu
tag: 18.04
layer: sha256:90497d4758cf4e8b22913aec17e82e30336584847dd956a3383efc949aba968a, size: 30641124
layer: sha256:2468b9e0fff8a0409adb672f8756e8920fbfa32763a44b4c9e3a6aecc26a6f85, size: 843
layer: sha256:37aeca5fb7ec932a26b18693ccb530e3fdf1e7d4c0e846946448e1537e0d9d7a, size: 473
layer: sha256:d3da7922cea78b56e9f974475499397f935eca546ff74383fff8bb975616263a, size: 860
layer: sha256:31842cf4229f29c1d242b3eefb523c7f6f5e65b350ca9baecf4ec02125ee489c, size: 162