'Converts a pixel to a longitude, latitude pair at the given zoom level.'

def pixel_to_lonlat(self, px, zoom):

    if (len(px) != 2):
        raise TypeError('Pixel    should    be    a    sequence    of    two    elements.')
    npix = self._npix[zoom]
    lon = ((px[0] - npix) / self._degpp[zoom])
    lat = (RTOD * ((2 * atan(exp(((px[1] - npix) / ((-1.0) * self._radpp[zoom]))))) - (0.5 * pi)))
    return (lon, lat)
