Expected behaviour

If the user imports a .ipynb to .py, executes cells without saving the .py, closes the .py file, imports a new .ipynb to .py, code lenses and the results of executing any cells in the new .py should be based on the new file contents.

Actual behaviour

Code lenses and the resultant execution are based on the old file contents.

Steps to reproduce:

1. On master, start the extension development host
2. Import a .ipynb into .py
3. Execute at least one cell so it shows up in the interactive window
4. Close the imported .py file and import a different .ipynb into .py
5. Execute some cells
6. The executed cells are from the previous .py file, and codelenses are rendered based on the previous file as well