I cannot find _Py_ForgetReference() or _Py_NewReference() in numpy
code base (I checked the master branch).

https://github.com/henjo/numpy/blob/cd73a18cdbdf679f2f74b7b21d2951bf124d80fb/numpy/core/src/multiarray/ucsnarrow.c#L96

That seems to be from a fork of numpy 1.6, which is quite old (2011?). Current master does not have that file at all.