code: def _InitializeParserObjects(self, parser_filter_expression=None):
      
      self._formats_with_signatures, non_sigscan_parser_names = (
          parsers_manager.ParsersManager.GetFormatsWithSignatures(
              parser_filter_expression=parser_filter_expression))
  
      self._non_sigscan_parser_names = []
      for parser_name in non_sigscan_parser_names:
        if parser_name not in ('filestat', 'usnjrnl'):
          self._non_sigscan_parser_names.append(parser_name)
  
      self._file_scanner = parsers_manager.ParsersManager.CreateSignatureScanner(
          self._formats_with_signatures)
  
      self._parsers = parsers_manager.ParsersManager.GetParserObjects(
          parser_filter_expression=parser_filter_expression)
  
      active_parser_names = ', '.join(sorted(self._parsers.keys()))
      logger.debug('Active parsers: {0:s}'.format(active_parser_names))
  
      self._filestat_parser = self._parsers.get('filestat', None)
      if 'filestat' in self._parsers:
        del self._parsers['filestat']
  
      self._mft_parser = self._parsers.get('mft', None)
  
      self._usnjrnl_parser = self._parsers.get('usnjrnl', None)
      if 'usnjrnl' in self._parsers:
        del self._parsers['usnjrnl']
docs: Initializes the parser objects.
  
      Args:
        parser_filter_expression (Optional[str]): the parser filter expression,
            None represents all parsers and plugins.
  
            The parser filter expression is a comma separated value string that
            denotes a list of parser names to include and/or exclude. Each entry
            can have the value of:
  
            * An exact match of a list of parsers, or a preset (see
              data/presets.yaml for the list of predefined presets).
            * A name of a single parser (case insensitive), e.g. msiecf.
            * A glob name for a single parser, e.g. '*msie*' (case insensitive).