def cortex_to_angle(self, x, y):
raise NotImplementedError(<EOL>'<STR_LIT>')<EOL>
model.cortex_to_angle(x, y) yields a vector of (polar-angle, eccentricity, id) corresponding
to the given (x,y) coordinates from a cortical map. The id that is returned is a positive
integer corresponding to an ROI label (e.g., V1, MT).
If x and y are vectors of length n then the return value is an (n x 3) matrix in which each
row corresponds to one (x,y) pair.