Box around text

I want to make a semi-transparent box around the text labels along the radial axis of a polar plot. Is there a method that returns the coordinates of a box that encloses the text?

I see that a text instance has a method called get_window_extent. What does it return? What would I use for the parameter 'renderer'? Are there any examples showing how to use this?

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Ms. Carol A. Leger
SRI International Phone: (650) 859-4114
333 Ravenswood Avenue G-273
Menlo Park, CA 94025 e-mail: leger@...392...