func (v *LessonCounter) VisitLessonTut(l *LessonTut) {
	v.count++
}
VisitLessonTut increments the count.
package model
type LessonCounter struct {
	count int
}
func NewTutorialLessonCounter() *LessonCounter {
	return &LessonCounter{0}
}
func (v *LessonCounter) Count() int {
	return v.count
}
func (v *LessonCounter) VisitBlockTut(b *BlockTut) {
}