Nipype 2.0 idea: interface assertions

[oesteban]

Summary

Assertions are a good programming in general. What if nipype included a language for interface-level assertions that are checked when the interface finished running?

Actual behavior

Right now, interfaces include only one low-level assertion: do output files of this interface exist in the prescribed path?

Expected behavior

An easy means to tell nipype things like:

• "is the output image empty?",
• "expected dtypes for output image files",
• "check that the x-forms matrices of the outputs.out_file output match the x-form matrices of inputs.reference_file".

These kind of checks would make debugging complex pipelines easier.

[satra]

@oesteban - as we improve the image handling traits classes, things like these can go into bothe input and output sides. added it to a 2.0 milestone.