ProcessingInputCollection deserialization classmethod

[greglucas]

This is more of a question / design discussion and very minor and doesn't need to be addressed, just something that I noticed so figured I would write it down.

It looks like we are creating an empty class and then calling desserialize on that. That seemed odd to me at first glance and I was wondering if it would instead be more appropriate as a classmethod?

my_instance = ProcessingInputCollection()
my_instance.deserialize(input_json)

to instead be:

my_instance = ProcessingInputCollection.deserialize(input_json)

(or it could be called from_json() for example)

I tried making this update, but there is a test for calling deserialize multiple times and expecting that to update the instance inplace. I wasn't sure whether that was needed or not, and if an alternative would be to always serialize/deserialize between a single object and then we could add an __add__ method if we wanted to combine collections together. But, I wasn't sure when we need to add collections together.

[maxinelasp]

I considered this when first running it, ultimately I decided if you wanted to add additional serialized input collections it would be annoying to have the class object. Now that we're using it, I suspect that case won't ever really happen anyway, so your __add__ idea would work in that case.