Why centropy concatenate features?

[Buiboni]

Hi,
I am trying to use the centropy function, however I don't understand the np.c_[x,y] (here). This concatenates x and y along the columns which are the features, but as far as I understand centropy should compute the conditional entropy of x relative to y. Hence we should be concatenating the rows (number of sample) instead... Shouldn't we?
Best,
A