passing user defined objects as an input

[djarecka]

I've been debugging code created by @harveyaa, and there is an issue when FunctionalImage is passed as an input. Even if we make sure that the image doesn't change during the execution, there is still issue with hash value. The task run fine, but because hash value is changing the task can't find the results.

In #432 I've added modified code from @harveyaa. I've also added a part to pydra to use cp.dumps to calculate the hash value for non-basic python objects and print statements to show where the hash value of img changes. It looks to me that ConcurrentFutures is responsible for this. Any idea?

[satra]

concurrent futures should not change the object. is the object itself being changed by the function that's using it?

[djarecka]

in original code it was changed, but not in the versioned i posted in #432