code: def _error_to_string(self, error_id):
          
          strerror = self.lib.iperf_strerror
          strerror.restype = c_char_p
          return strerror(error_id).decode('utf-8')
docs: Returns an error string from libiperf
  
          :param error_id: The error_id produced by libiperf
          :rtype: string