code: def create_unique_wcsname(fimg, extnum, wcsname):
      
      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
docs: 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