text: from django.db import models
  from apps.authentication.models import User
  from .element import Element
  
  
  class Scheme(models.Model):
      """Схема"""
  
      name = models.CharField('Название', max_length=255)
      creator = models.ForeignKey(User, on_delete=models.CASCADE, verbose_name='Создатель')
      formula = models.CharField('Формула', max_length=255, blank=True, null=True)
      elements = models.ManyToManyField(Element, 'schemes', through='SchemeElement')
  
      def __str__(self):
          return self.name
  
      class Meta:
          verbose_name = 'Схема'
          verbose_name_plural = 'Схемы'
  