[Insight-developers] Advice on filter writing -- 2 arrays of images as inputs?

[kent williams]

I have been assigned the task of converting one of those faux-ITK filters
that people write -- you know, where they have SetInput(s), Update() and
GetOutput(s) but it's not actually a pipeline-compatible filter -- into an
actual ITK filter.

What's blowing my mind about it is that as it stands, it takes as inputs two
arrays of images. Not an itk::Array or itk::Vector, but a homegrown array
class.  

My question is this: What is the most ITK-esque way to handle two sets of
multiple image inputs?  SetNthInput seems fine for a class with only one
array of homogenous inputs, but I don't know what to do with a second array.