code: func (s *FixedSchema) MarshalJSON() ([]byte, error) {
  	return json.Marshal(struct {
  		Type string `json:"type,omitempty"`
  		Size int    `json:"size,omitempty"`
  		Name string `json:"name,omitempty"`
  	}{
  		Type: "fixed",
  		Size: s.Size,
  		Name: s.Name,
  	})
  }
docs: // MarshalJSON serializes the given schema as JSON.