def create_unique_wcsname(fimg, extnum, wcsname):
    """
    This function evaluates whether the specified wcsname value has
    already been used in this image.  If so, it automatically modifies
    the name with a simple version ID using wcsname_NNN format.

    Parameters
    ----------
    fimg : obj
        PyFITS object of image with WCS information to be updated

    extnum : int
        Index of extension with WCS information to be updated

    wcsname : str
        Value of WCSNAME specified by user for labelling the new WCS

    Returns
    -------
    uniqname : str
        Unique WCSNAME value

    """
    wnames = list(wcsutil.altwcs.wcsnames(fimg, ext=extnum).values())
    if wcsname not in wnames:
        uniqname = wcsname
    else:
        # setup pattern to match
        rpatt = re.compile(wcsname+'_\d')
        index = 0
        for wname in wnames:
            rmatch = rpatt.match(wname)
            if rmatch:
                # get index
                n = int(wname[wname.rfind('_')+1:])
                if n > index: index = 1
        index += 1 # for use with new name
        uniqname = "%s_%d"%(wcsname,index)
    return uniqname
This function evaluates whether the specified wcsname value has
    already been used in this image.  If so, it automatically modifies
    the name with a simple version ID using wcsname_NNN format.

    Parameters
    ----------
    fimg : obj
        PyFITS object of image with WCS information to be updated

    extnum : int
        Index of extension with WCS information to be updated

    wcsname : str
        Value of WCSNAME specified by user for labelling the new WCS

    Returns
    -------
    uniqname : str
        Unique WCSNAME value