[Python] numpy.hstack gives: TypeError: _vhstack_dispatcher() takes 1 positional argument but...

I have this python code that takes in Nx2 numpy array in which each row represents the [x,y] coordinates of one of the N points, and it returns an array of the same size containing transformed [u,v] coordinates for each point.

def inverse(arr):
return np.hstack([arr[:, 0:1], arr[:, 1:2] - arr[:, 0:1]**2])


The transformation is defined as

u = x
v = y - x^2


This code works fine. But then I have the transformation

u = sqrt(x^2 + y^2)
v = arctan2(y, x)


And the code is

def inverse(arr):
return np.hstack(np.sqrt(arr[:, 0:1]**2 + arr[:, 1:2]**2), np.arctan2(arr[:, 1:2], arr[:, 0:1]))


But this code gives the following error:

TypeError: _vhstack_dispatcher() takes 1 positional argument but 2 were given


What could be the reason for this? How can I fix this?

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