docs: def world2pix(self, ra, dec, usepv=True):
          """
          Convert a given RA/DEC position to the  X/Y/HDULIST_INDEX in the cutout frame.
  
           Here we loop over the hdulist to find the extension is RA/DEC are from and then return the appropriate X/Y
          :param ra: The Right Ascension of the point
          :type ra: Quantity
          :param dec: The Declination of the point
          :type dec: Quantity
          :return: X, Y, Extension position of source in cutout reference frame
          :rtype: (float, float, int)
          @param usepv: Should the non-linear part of the WCS be using to compute the transformation? (default: True)
          """
          x, y, idx = (0, 0, 0)
          for idx in range(1, len(self.hdulist)):
              hdu = self.hdulist[idx]
              x, y = hdu.wcs.sky2xy(ra, dec, usepv=usepv)
              if 0 < x < hdu.header['NAXIS1'] and 0 < y < hdu.header['NAXIS2']:
                  # print "Inside the frame."
                  return x, y, idx
          return x, y, idx