Setting Key Types for Shapekey Interpolation in Python

I would like to set the Key Type variable for shapekey IPO curves in a Python script. This is the varibale that controls how absolute shape keys are interpolated. I am working with absolute shapekeys and would like to change the default Cardinal Key Type to Linear. This can be done in the GUI in the Shape IPO window under the curves option:

http://wiki.blender.org/index.php/Manual/Absolute_Shape_Keys