getting the parent bone's name from a child_of constraint


given Mesh that has a child_of constraint wich connects it to a bone I could use the following code to get that bones name in Blender 2.49

for c in mesh.Constraints:
if c.type = ‘CHILD_OF’

the c.getitem(Constraint.Settings.BONE) part does not work in Blender 2.57. How should i do it instead?

Thnx in Advance!