code: def GetFormattedField(self, event, field_name):
      
      callback_name = self._FIELD_FORMAT_CALLBACKS.get(field_name, None)
      callback_function = None
      if callback_name:
        callback_function = getattr(self, callback_name, None)
  
      if callback_function:
        output_value = callback_function(event)
      else:
        output_value = getattr(event, field_name, '-')
  
      if output_value is None:
        output_value = '-'
  
      elif not isinstance(output_value, py2to3.STRING_TYPES):
        output_value = '{0!s}'.format(output_value)
  
      return output_value
docs: Formats the specified field.
  
      Args:
        event (EventObject): event.
        field_name (str): name of the field.
  
      Returns:
        str: value of the field.