code: func (wc *WhisperClient) GetFilterMessages(ctx *Context, id string) (*Messages, error) {
  	rawFilterMessages, err := wc.client.FilterMessages(ctx.context, id)
  	if err != nil {
  		return nil, err
  	}
  	res := make([]*whisper.Message, len(rawFilterMessages))
  	copy(res, rawFilterMessages)
  	return &Messages{res}, nil
  }
docs: // GetFilterMessages retrieves all messages that are received between the last call to
  // this function and match the criteria that where given when the filter was created.