text: function toStringExtension() {
      class Person {
          constructor(name, email) {
              this.name = name
              this.email = email
          }
  
          toString() {
              let className = this.constructor.name
              return `${className} (name: ${this.name}, email: ${this.email})`
          }
      }
  
      class Teacher extends Person {
          constructor(name, email, subject) {
              super(name, email)
              this.subject = subject
          }
  
          toString() {
              let personToStr = super.toString().slice(0, -1)
              return personToStr + `, subject: ${this.subject})`
          }
      }
  
      class Student extends Person {
          constructor(name, email, course) {
              super(name, email)
              this.course = course
          }
  
          toString() {
              let personToStr = super.toString().slice(0, -1)
              return personToStr + `, course: ${this.course})`
          }
      }
  
      return {Person, Teacher, Student}
  }
  
  let obj = toStringExtension()
  
  const Person = obj.Person
  const Teacher = obj.Teacher
  const Student = obj.Student
  
  let p = new Person('Ivan', 'vankata@gosy.bg')
  console.log(p + '')
  
  let t = new Teacher('Pesho', 'pesho@abv.bg', 'Java')
  console.log(t + '')
  
  let s = new Student('Stamat', 'stamat@beast.bg', 'php')
  console.log(s + '')
  
  module.exports = Person