code: def parse(self, **kwargs):
          
          try:
              output_folder = self.retrieved
          except exceptions.NotExistent:
              return self.exit_codes.ERROR_NO_RETRIEVED_FOLDER
  
          filename_stdout = self.node.get_attribute('output_filename')
          filename_stderr = self.node.get_attribute('error_filename')
  
          try:
              with output_folder.open(filename_stderr, 'r') as handle:
                  exit_code = self.parse_stderr(handle)
          except (OSError, IOError):
              self.logger.exception('Failed to read the stderr file\n%s', traceback.format_exc())
              return self.exit_codes.ERROR_READING_ERROR_FILE
  
          if exit_code:
              return exit_code
  
          try:
              with output_folder.open(filename_stdout, 'r') as handle:
                  handle.seek(0)
                  exit_code = self.parse_stdout(handle)
          except (OSError, IOError):
              self.logger.exception('Failed to read the stdout file\n%s', traceback.format_exc())
              return self.exit_codes.ERROR_READING_OUTPUT_FILE
  
          if exit_code:
              return exit_code
docs: Parse the contents of the output files retrieved in the `FolderData`.