def _ParseFileData(self, knowledge_base, file_object):
    """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.
    """
    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)
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.