Error by python script: Cannot set read-only property ---


I did some changes in the project by modifying the constitutive model from MC to HS. More parameters were required for HS. I am trying to set the values of Gref as     g_i.Materials[x].Gref = Gparameter, but getting the error as cannot set a read-only property Gref. Kindly suggest me how to handle this problem. 

thanks in anticipation. 

Best Regards 

Gulnaz Shahzadi