def from_meminfo(cls, context, builder, set_type, meminfo):
        """
        Allocate a new set instance pointing to an existing payload
        (a meminfo pointer).
        Note the parent field has to be filled by the caller.
        """
        self = cls(context, builder, set_type, None)
        self._set.meminfo = meminfo
        self._set.parent = context.get_constant_null(types.pyobject)
        context.nrt.incref(builder, set_type, self.value)
        # Payload is part of the meminfo, no need to touch it
        return self

        Allocate a new set instance pointing to an existing payload
        (a meminfo pointer).
        Note the parent field has to be filled by the caller.
        
numba/cpython/setobj.py