docs: def create_mef(filename=None):
      """
      Create a file an MEF fits file called filename.  Generate a random
      filename if None given
      """
      import pyfits, time
  
      if not filename:
          ### here I know what filename is to start with.
          import tempfile
          filename=tempfile.mktemp(suffix='.fits')
      else:
          import string, re
          ### filenames gotta be a string and no lead/trailing space
          filename=string.strip(str(filename))
          ### require that the filename ends in .fits
          suffix=re.match(r'^.*.fits$',filename)
          if not suffix:
              filename = filename+'.fits'
  
      ### create an HDU list
      temp = pyfits.HDUList()
  
      ### create a primary HDU
      prihdu = pyfits.PrimaryHDU()
  
      ### build the header
      h=prihdu.header
      h.update('EXTEND',pyfits.TRUE,after='NAXIS')
      h.update('NEXTEND',0,after='EXTEND')
      h.add_comment('MEF created at CADC')
      h.add_comment('Created using '+__name__+' '+__Version__)
      h.add_comment('Extensions may not be in CCD order')
      #h.update('cfh12k',__Version__,comment='split2mef software at CADC')
      h.add_comment('Use the EXTNAME keyword')
      h.add_history('Primary HDU created on '+time.asctime())
  
      ### stick the HDU onto the HDU list and write to file
      temp.append(prihdu)
      temp.writeto(filename)
      temp.close()
  
      return(filename)