Hi, 

I am using python to calculate contact area between 2 chains. My code is as follows

p1, p2 = [s.surface_piece for s in openModels.list(modelTypes=[MSMSModel])]
y = measure.contact_area(p1, p2, 2.5)

However, this returns the error: TypeError: contact_area() takes at least 4 arguments (3 given)

This is the function for contact_area

def contact_area(p1, p2, d, color = None, offset = None, slab = None, smooth = False, optimize = True):

What is the 4th required argument?

Best,

Kevin