code: func (m *ImagemapMessage) MarshalJSON() ([]byte, error) {
  	return json.Marshal(&struct {
  		Type       MessageType      `json:"type"`
  		BaseURL    string           `json:"baseUrl"`
  		AltText    string           `json:"altText"`
  		BaseSize   ImagemapBaseSize `json:"baseSize"`
  		Actions    []ImagemapAction `json:"actions"`
  		Video      *ImagemapVideo   `json:"video,omitempty"`
  		QuickReply *QuickReplyItems `json:"quickReply,omitempty"`
  	}{
  		Type:       MessageTypeImagemap,
  		BaseURL:    m.BaseURL,
  		AltText:    m.AltText,
  		BaseSize:   m.BaseSize,
  		Actions:    m.Actions,
  		Video:      m.Video,
  		QuickReply: m.quickReplyitems,
  	})
  }
docs: // MarshalJSON method of ImagemapMessage