See repro test here.
When we create a new network, podman returns its id. However, the Network.id method tries to return self.attrs["Id"], but that always fails, so it falls back to returing a synthetic id based on the network name. If we pass this id to network.get(), the call fails, since Podman does not know any networks with that id.
Lowercasing Id -> id in this line fixes the issue, and causes Network.id to return the correct id assiged by Podman. But I'm not sure if that's the correct fix.