Question for Set Intersection Example

[heqianjane88]

Hi,
I got this error for the set intersection protocol: AttributeError: 'Compare' object has no attribute 'i'
It may be related to this part of the code.
# compute intersection of c.X and c.barY
for e in c.X:
if e in c.barY:
c.output(e, desc="in output set")

Do you have any clue how to fix it? Thanks very much!