func (r Rune) Present() bool {
	return r.value != nil
}
Present returns whether or not the value is present.
package optional
import (
	"encoding/json"
	"errors"
)
type Rune struct {
	value *rune
}
func NewRune(v rune) Rune {
	return Rune{&v}
}
func (r *Rune) Set(v rune) {
	r.value = &v
}
func (r Rune) Get() (rune, error) {
	if !r.Present() {
		var zero rune
		return zero, errors.New("value not present")
	}
	return *r.value, nil
}
func (r Rune) MustGet() rune {
	if !r.Present() {
		panic("value not present")
	}
	return *r.value
}