code: def _ParseFileData(self, knowledge_base, file_object):
      
      text_file_object = dfvfs_text_file.TextFile(file_object, encoding='utf-8')
  
      system_product = text_file_object.readline()
  
      # Only parse known default /etc/issue file contents.
      if system_product.startswith('Debian GNU/Linux '):
        system_product, _, _ = system_product.partition('\\')
        system_product = system_product.rstrip()
  
      else:
        system_product = None
  
      if not knowledge_base.GetValue('operating_system_product'):
        if system_product:
          knowledge_base.SetValue('operating_system_product', system_product)
docs: Parses file content (data) for system product preprocessing attribute.
  
      Args:
        knowledge_base (KnowledgeBase): to fill with preprocessing information.
        file_object (dfvfs.FileIO): file-like object that contains the artifact
            value data.
  
      Raises:
        errors.PreProcessFail: if the preprocessing fails.