<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def add_file(self, filename, file_content):
 """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. """

        self._group_data['fileName'] = filename
        self._file_content = file_content