def save_thread(self):
        """
        Release the GIL and return the former thread state
        (an opaque non-NULL pointer).
        """
        fnty = ir.FunctionType(self.voidptr, [])
        fn = self._get_function(fnty, name="PyEval_SaveThread")
        return self.builder.call(fn, [])

        Release the GIL and return the former thread state
        (an opaque non-NULL pointer).
        
numba/core/pythonapi.py