TVM code problem

There is a problem that I can’t understand, as shown in the figure below.

The function “init_by_constructor” ’s definition is “None”,how is it implemented?

I’m appreciate that you can help me to sovle my doubt!

please search “_object.init_by_constructor = init_handle_by_constructor” in file packed_func.py

Thank you very much for your answer which solved my confusion!