Error: IndexError: index 1 is out of bounds for dimension with size 1

import mindspore as ms
import mindspore.nn as nn
import mindspore.ops as ops
from mindspore import Tensor


class ConditionalNet(nn.Cell):
    def __init__(self):
        super().__init__()
        self.bool_list = Tensor([True, False])  # works ok if self.bool_list = [True, False]
        self.y = Tensor([1])
        self.z = Tensor([3, 4])

    def construct(self):
        output = []
        for i in range(len(self.bool_list)):
            if self.bool_list[i]:
                output.append(self.y[i])
            else:
                output.append(self.z[i])
        return ops.stack(output)

if __name__ == '__main__':
    ms.set_context(mode=ms.GRAPH_MODE)
    net = ConditionalNet()
    print(net())  # expected: 1, 4