In the future I will post on the pylearn-users user group, but I'll continue the thread here for continuity.

To be clearer, I have been passing Null (without quotation marks) in my yaml source and the following error is raised:

TypeError: received None as the value for the key act_dec

I have also tried as suggested passing null (not capitalized, no quotes) and the error is the same. Is there another way of specifying None in yaml? I have had no problems running the same yaml scripts before this merge.

It seems that the lines 345-349 prevent using None as a kw arg when it is sometimes necessary to do so.

Thanks!
--Andy