code: def _GetEventLogProviderKey(self, log_source):
      
      table_names = ['event_log_providers']
      column_names = ['event_log_provider_key']
      condition = 'log_source == "{0:s}"'.format(log_source)
  
      values_list = list(self._database_file.GetValues(
          table_names, column_names, condition))
  
      number_of_values = len(values_list)
      if number_of_values == 0:
        return None
  
      if number_of_values == 1:
        values = values_list[0]
        return values['event_log_provider_key']
  
      raise RuntimeError('More than one value found in database.')
docs: Retrieves the Event Log provider key.
  
      Args:
        log_source (str): Event Log source.
  
      Returns:
        str: Event Log provider key or None if not available.
  
      Raises:
        RuntimeError: if more than one value is found in the database.