code: def ComputeFortranSuffixes(suffixes, ppsuffixes):
      
      assert len(suffixes) > 0
      s = suffixes[0]
      sup = s.upper()
      upper_suffixes = [_.upper() for _ in suffixes]
      if SCons.Util.case_sensitive_suffixes(s, sup):
          ppsuffixes.extend(upper_suffixes)
      else:
          suffixes.extend(upper_suffixes)
docs: suffixes are fortran source files, and ppsuffixes the ones to be
      pre-processed. Both should be sequences, not strings.