code: def _GetEventIdentifiers(self, event):
      attributes = []
      attribute_string = 'data_type: {0:s}'.format(event.data_type)
      attributes.append(attribute_string)
      for attribute_name, attribute_value in sorted(event.GetAttributes()):
        if attribute_name in self._IDENTIFIER_EXCLUDED_ATTRIBUTES:
          continue
        if not attribute_value:
          continue
        if attribute_name == 'pathspec':
          attribute_value = attribute_value.comparable
        elif isinstance(attribute_value, dict):
          attribute_value = sorted(attribute_value.items())
        elif isinstance(attribute_value, set):
          attribute_value = sorted(list(attribute_value))
        elif isinstance(attribute_value, py2to3.BYTES_TYPE):
          attribute_value = repr(attribute_value)
        try:
          attribute_string = '{0:s}: {1!s}'.format(
              attribute_name, attribute_value)
        except UnicodeDecodeError:
          logger.error('Failed to decode attribute {0:s}'.format(
              attribute_name))
        attributes.append(attribute_string)
      if event.timestamp_desc in (
          'atime', 'ctime', 'crtime', 'mtime',
          definitions.TIME_DESCRIPTION_LAST_ACCESS,
          definitions.TIME_DESCRIPTION_CHANGE,
          definitions.TIME_DESCRIPTION_CREATION,
          definitions.TIME_DESCRIPTION_MODIFICATION):
        macb_group_identifier = ', '.join(attributes)
      else:
        macb_group_identifier = None
      attributes.insert(0, event.timestamp_desc)
      content_identifier = ', '.join(attributes)
      return macb_group_identifier, content_identifier