Sage Notebook: Add New Method to Evaluate All Cells with ...

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In the Sage Notebook there is a drop down menu that allows one to choose the program for evaluating the cells in the workbook.

I'd like to add a new method to this menu. Basically, I want the option to evaluate all cells with Enthought Python.

I realize this will involve hacking the source code. I'm wondering if someone can point me to the relevant source files.