code: def add_file(self, filename, file_content):
          
          self._group_data['fileName'] = filename
          self._file_content = file_content
docs: Add a file for Document and Report types.
  
          Example::
  
              document = tcex.batch.group('Document', 'My Document')
              document.add_file('my_file.txt', 'my contents')
  
          Args:
              filename (str): The name of the file.
              file_content (bytes|method|str): The contents of the file or callback to get contents.