code: def string_result(result, func, arguments):
      
      if result:
          # make a python string copy
          s = bytes_to_str(ctypes.string_at(result))
          # free original string ptr
          libvlc_free(result)
          return s
      return None
docs: Errcheck function. Returns a string and frees the original pointer.
  
      It assumes the result is a char *.