Minor docfix to kappa.py
Minor docfix to kappa.py

neurord/pysb,d-fan/pysb,pysb/pysb,johnbachman/pysb,spgarbet/pysb,LoLab-VU/pysb,neurord/pysb,neurord/pysb,d-fan/pysb,LoLab-VU/pysb,jmuhlich/pysb,d-fan/pysb,johnbachman/pysb,alubbock/pysb,spgarbet/pysb,spgarbet/pysb