def _guard_with_as(self, state):
        """Checks if the next instruction after a SETUP_WITH is something other
        than a POP_TOP, if it is something else it'll be some sort of store
        which is not supported (this corresponds to `with CTXMGR as VAR(S)`)."""
        current_inst = state.get_inst()
        if current_inst.opname in {"SETUP_WITH", "BEFORE_WITH"}:
            next_op = self._bytecode[current_inst.next].opname
            if next_op != "POP_TOP":
                msg = ("The 'with (context manager) as "
                       "(variable):' construct is not "
                       "supported.")
                raise UnsupportedBytecodeError(msg)
Checks if the next instruction after a SETUP_WITH is something other
        than a POP_TOP, if it is something else it'll be some sort of store
        which is not supported (this corresponds to `with CTXMGR as VAR(S)`).
numba/core/byteflow.py