Problem and error message with one of blender's operators

Hi all,

I’m having a problem with one of blender’s operators, specifically this one: bpy.ops.constraint.childof_set_inverse

When I try calling that operator, I get an error message:

The cube is the active object and the one with the constraint on it. What does the message Context missing ‘constraint’ mean? How, why, and where am I failing at calling this operator?

BTW, did I mention I’m not that good with python?