def METHOD_NAME(self, request):
    batch = Batch()
    spec = self.spec[ArrayKeys.A]
    spec.roi = request[ArrayKeys.A].roi
    batch.arrays[ArrayKeys.A] = Array(
        np.array([[0, 1], [2, 3]], dtype=np.float32), spec
    )
    spec = self.spec[ArrayKeys.B]
    spec.roi = request[ArrayKeys.B].roi
    batch.arrays[ArrayKeys.B] = Array(
        np.array([[0, 1], [2, 3]], dtype=np.float32), spec
    )
    return batch