docs: def find_detrend_keyword(header, type):
      """Search through header and find
      the elixir formated string(s) that match the the
      input 'type'.
  
      header is a FITS HDU.
      Elixir formated strings are crunid.type.filter/exptime.chipid.version.
      """
      import re, string
      value='NULL'
      #print type
      for h in header:
          g = str(h)
          if ( string.find(g,'.'+type+'.')!= -1 ):
              result=re.search('[^\s]*\.'+type+'\.[^\s]*\.\d\d\.\d\d',g)
              if result:
                  return result.group(0)