How to calculate g-function using pygfunction for GSHP modeling in Energyplus

edit

I try to model ground-source heat pump systems in EnergyPlus. And I want to use my configuration of borehole, without use value of example files in EnergyPlus. So, I have to get g-function by using pygfunction to input 'GorundHeatExchanger:ResponseFactors'. I try to calculate g-function using pygfunction, but I took just graph of g-function, not value of g-function g value, ln(T/Ts) value which is neccesary value to model GSHP system in EnergyPlus. Please let me know how to get g-function value by using pygfunction. If you can, I want to get some tips or code for calculation of g-function. Thanks a lot.