def null(cls, loc):
        """
        A node for null value.

        This node is not handled by type inference. It is only added by
        post-typing passes.
        """
        assert isinstance(loc, Loc)
        op = 'null'
        return cls(op=op, loc=loc)

        A node for null value.

        This node is not handled by type inference. It is only added by
        post-typing passes.
        
numba/core/ir.py