Intra-class correlation in nipype

Hi Experts,

I encountered difficulty to use the icc.ICC function from nipype.algorithmn.
I wonder if anyone used this function and might answer my question below.

How should I specify the inputs for different sessions?
This is the help explanation below.
subjects_sessions: (a list of items which are a list of items which
are a pathlike object or string representing an existing file)
n subjects m sessions 3D stat files
mask: (a pathlike object or string representing an existing file)

Thanks!

Yun