code: def createWcsHDU(self):
          
          hdu = fits.ImageHDU()
          hdu.header['EXTNAME'] = 'WCS'
          hdu.header['EXTVER'] = 1
          # Now, update original image size information
          hdu.header['WCSAXES'] = (2, "number of World Coordinate System axes")
          hdu.header['NPIX1'] = (self.naxis1, "Length of array axis 1")
          hdu.header['NPIX2'] = (self.naxis2, "Length of array axis 2")
          hdu.header['PIXVALUE'] = (0.0, "values of pixels in array")
  
          # Write out values to header...
          excluded_keys = ['naxis1','naxis2']
          for key in self.wcskeys:
              _dkey = self.wcstrans[key]
              if _dkey not in excluded_keys:
                  hdu.header[key] = self.__dict__[_dkey]
  
  
          return hdu
docs: Generate a WCS header object that can be used to
              populate a reference WCS HDU.