Add __returns__ attribute to PolynomialModel.
Add __returns__ attribute to PolynomialModel.

qPCR4vir/orange3,cheral/orange3,cheral/orange3,qPCR4vir/orange3,qPCR4vir/orange3,cheral/orange3,qPCR4vir/orange3,cheral/orange3,cheral/orange3,cheral/orange3,qPCR4vir/orange3,qPCR4vir/orange3