How to use the drizzlepac.updatehdr.updatewcs_with_shift function in drizzlepac

def apply_tweak_shifts(wcs_ref, shift_dict, grism_matches={}, verbose=True):
    """
    
    """
    from drizzlepac import updatehdr

    hdu = wcs_ref.to_fits(relax=True)
    file0 = list(shift_dict.keys())[0].split('.fits')[0]
    tweak_file = '{0}_tweak_wcs.fits'.format(file0)
    hdu.writeto(tweak_file, clobber=True)
    for file in shift_dict:
        updatehdr.updatewcs_with_shift(file, tweak_file,
                                        xsh=shift_dict[file][0],
                                        ysh=shift_dict[file][1],
                                        rot=0., scale=1.,
                                        wcsname='SHIFT', force=True,
                                        reusename=True, verbose=verbose,
                                        sciext='SCI')
        
        ### Bug in astrodrizzle? Dies if the FLT files don't have MJD-OBS
        ### keywords
        im = pyfits.open(file, mode='update')
        im[0].header['MJD-OBS'] = im[0].header['EXPSTART']
        im.flush()
        
        # Update paired grism exposures
        if file in grism_matches:
            for grism_file in grism_matches[file]:

for drz_file in drz_files[1:]:
        root = drz_file.split('_drz')[0]
        result = align_drizzled_image(root=root, mag_limits=mag_limits,
                                      radec=rd_ref,
                                      NITER=5, clip=20)

        orig_wcs, drz_wcs, out_shift, out_rot, out_scale = result
        
        im = pyfits.open(drz_file)
        files = []
        for i in range(im[0].header['NDRIZIM']):
          files.append(im[0].header['D{0:03d}DATA'.format(i+1)].split('[')[0])
        
        
        for file in files:
            updatehdr.updatewcs_with_shift(file, drz_files[0],
                                      xsh=out_shift[0], ysh=out_shift[1],
                                      rot=out_rot, scale=out_scale,
                                      wcsname=ref_catalog, force=True,
                                      reusename=True, verbose=True,
                                      sciext='SCI')

            im = pyfits.open(file, mode='update')
            im[0].header['MJD-OBS'] = im[0].header['EXPSTART']
            im.flush()

        ### Second drizzle
        if len(files) > 1:
            AstroDrizzle(files, output=root, clean=True, context=False, preserve=False, skysub=True, driz_separate=False, driz_sep_wcs=False, median=False, blot=False, driz_cr=False, driz_cr_corr=False, driz_combine=True, final_bits=576, coeffs=True, resetbits=0, build=False, final_wht_type='IVM')        
        else:
            AstroDrizzle(files, output=root, clean=True, final_scale=None, final_pixfrac=1, context=False, final_bits=576, preserve=False, driz_separate=False, driz_sep_wcs=False, median=False, blot=False, driz_cr=False, driz_cr_corr=False, driz_combine=True, build=False, final_wht_type='IVM')

im[0].header['MJD-OBS'] = im[0].header['EXPSTART']
            im.flush()
        
        return True
        
    #### Get from WCS log file
    for ext in wcs_log['ext']:
        tmp_wcs = '/tmp/{0}_tmpwcs.fits'.format(str(direct['product']))
        wcs_hdu[ext].writeto(tmp_wcs, clobber=True)
        if 'scale' in wcs_log.colnames:
            scale = wcs_log['scale'][ext]
        else:
            scale = 1.
            
        for file in grism['files']:
            updatehdr.updatewcs_with_shift(file, tmp_wcs,
                                      xsh=wcs_log['xshift'][ext],
                                      ysh=wcs_log['yshift'][ext],
                                      rot=wcs_log['rot'][ext], scale=scale,
                                      wcsname=ref_catalog, force=True,
                                      reusename=True, verbose=True,
                                      sciext='SCI')
            
            ### Bug in astrodrizzle? Dies if the FLT files don't have MJD-OBS
            ### keywords
            im = pyfits.open(file, mode='update')
            im[0].header['MJD-OBS'] = im[0].header['EXPSTART']
            im.flush()
            
    ### Bug in astrodrizzle? Dies if the FLT files don't have MJD-OBS
    ### keywords
    for file in grism['files']: