def getZernike(self, index):
if index not in list(self._dictCache.keys()):<EOL><INDENT>self._dictCache[index]= self._polar(index, self._rhoMap,<EOL>self._thetaMap)<EOL><DEDENT>return self._dictCache[index]<EOL>
getZernike

        Retrieve a map representing the index-th Zernike polynomial

        Args:
            index (int): The index of Zernike map to be generated,
                following Noll 1976 ordering.

        Returns:
            np.array: A map representing the index-th Zernike polynomial