Function expand_to_same_dims

ciphercore-base/src/ops/comparisons.rs:271–278

As we support broadcasting in comparison arguments, we need to make sure they are still broadcastable after bits are pulled out to the outermost dimension. Say, we want to compare array of size `[2, 3, 64]` and array of size `[3, 64]`. This is a valid operation because `[3, 64]` could be broadcasted to `[2, 3, 64]`. After pulling out bits, we get shapes `[64, 2, 3]` and `[64, 3]`, which are not

(a: Node, b: Node)

/// To fix this, we convert `[3, 64]` into `[1, 3, 64]` first. After pulling out
/// bits, shape is `[64, 1, 3]`, which could be broadcasted to `[64, 2, 3]`.
fn expand_to_same_dims(a: Node, b: Node) -> Result<(Node, Node)> {
    let len_a = a.get_type()?.get_shape().len();
    let len_b = b.get_type()?.get_shape().len();
    let result_len = max(len_a, len_b);
    let a = expand_dims(a, &(0..result_len - len_a).collect::<Vec<_>>())?;
    let b = expand_dims(b, &(0..result_len - len_b).collect::<Vec<_>>())?;
    Ok((a, b))
}

/// - This function flips all values of the input Array's last component,
/// which correspond to MSB bit (after `pull_out_bits`), to enable the