item() {
        const this_data = this.data;
        if (this_data.length !== 1) {
            throw new Error(`a Tensor with ${this_data.length} elements cannot be converted to Scalar`);
        }
        return this_data[0];
    }
Returns the value of this tensor as a standard JavaScript Number. This only works
for tensors with one element. For other cases, see `Tensor.tolist()`.
@returns {number|bigint} The value of this tensor as a standard JavaScript Number.
@throws {Error} If the tensor has more than one element.