[Closed] Add PF to ParticleSkinner

How to add a pf source to a particleskinner modifier?

pfs = pf_source()
 mybox = box()
 ps = particle_skinner()
 addmodifier mybox ps
 ps.Particle_Flow_Systems = #(pfs)

This code gives me the following error in Max 2015:

– Error occurred in anonymous codeblock; filename: ; position: 114; line: 5
– Runtime error: Invalid value for property: $PF_Source:PF Source 001 @ [0.000000,0.000000,0.000000]