code: func (c *BoxComponent) MarshalJSON() ([]byte, error) {
  	return json.Marshal(&struct {
  		Type     FlexComponentType        `json:"type"`
  		Layout   FlexBoxLayoutType        `json:"layout"`
  		Contents []FlexComponent          `json:"contents"`
  		Flex     *int                     `json:"flex,omitempty"`
  		Spacing  FlexComponentSpacingType `json:"spacing,omitempty"`
  		Margin   FlexComponentMarginType  `json:"margin,omitempty"`
  	}{
  		Type:     FlexComponentTypeBox,
  		Layout:   c.Layout,
  		Contents: c.Contents,
  		Flex:     c.Flex,
  		Spacing:  c.Spacing,
  		Margin:   c.Margin,
  	})
  }
docs: // MarshalJSON method of BoxComponent