import error

For some imported notebook, say demo1
`import ipynb.fs.defs.demo1` is OK, but `import ipynb.fs.defs.demo1 as d1` FAIL

and for other imported notebook, say demo2
`import ipynb.fs.defs.demo2 as d2` is OK, but `import ipynb.fs.defs.demo2` FAIL

Reproduce the two reported cases using the import entry point `ipynb.fs.defs` with `demo1` and `demo2`. Trace how the importer handles plain imports versus imports with `as`, then add coverage for both forms and confirm that each reported import succeeds consistently.

Escrito por el modelo de indexación a partir del texto del issue.