Include return statements in autocomplete signature

[carlthome]

When pressing shift-tab you get a very neat autocomplete box with a function's arguments. Would it be possible to also include return statements?

In the case of multiple returns, I imagine all branches would be listed. As returned objects don't have names in the outer scope, I imagine just taking the last local name if it exists (tricky) or the type() at the return statement.

[takluyver]

We don't have an easy way to get the type of the return variable without running the function, and I'm not sure that the internal name tells you much.

We'd encourage authors to document the return type either in the docstring or in function annotations - both of which should already be shown.