I was going through the source for hough transform in skimg library. I am not understanding why they have limited the value of $\theta$ from $-\pi/2$ to $\pi/2$.
Why can't they consider all $2\pi$ radians to detect the lines? For example, consider a line cutting through the second quadrant ((x1, y1) = (-3, 0) and (x2, y2) = (0, 3)). Here the $\theta$ > $\pi/2$. Why are all these lines being ignored?