I'm trying to do something a little unorthodox with the autorig, I'd like to save an unlocked modified copy of the quadruped leg inside another otherwise empty digital asset, then reference the parameters from the original quadruped leg rig.

This seems like it will work, however I'm trying to copy these parameters with python. I have written and tested the scripts I need to do these tasks, but I'm getting some errors when referencing the channels with python. Could someone point me in the right direction on what might be a possible cause of this error?

Traceback (most recent call last):
File “<console>”, line 1, in <module>
File “hou.session”, line 9, in copyParms
File “Ccygwin/home/prisms/builder-new/NightlyHEAD/dev/hfs/houdini/scripts/python\hou.py”, line 13368, in set
return _hou.Parm_set(*args)
ValueError: invalid null reference in method ‘Parm_set’, argument 2 of type ‘HOM_Parm &’

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an alternative to this would be making the auto rig leg more flexible (or explaining a better way to modify it). It doesn't have bones in a convenient way to make a proper horse leg. I kind of like the setup, I'd just like to modify it a little bit according to what I need.