old_contents: # coding=utf-8
  from django.db import models
  from django.contrib.auth.models import User
  
  from .base import LifeTimeTrackingModel
  
  class FacilitatorGuide(LifeTimeTrackingModel):
      user = models.ForeignKey(User, on_delete=models.SET_NULL, null=True)
      study_group = models.ForeignKey('studygroups.StudyGroup', on_delete=models.SET_NULL, null=True)
      course = models.ForeignKey('studygroups.Course', on_delete=models.CASCADE)
      title = models.CharField(max_length=256)
      caption = models.CharField(max_length=512)
      link = models.URLField()
      image = models.ImageField(blank=True)
  
      def __str__(self):
          return self.title
  
new_contents: # coding=utf-8
  from django.db import models
  from django.contrib.auth.models import User
  
  from .base import LifeTimeTrackingModel
  
  class FacilitatorGuide(LifeTimeTrackingModel):
      user = models.ForeignKey(User, on_delete=models.SET_NULL, null=True, blank=True)
      study_group = models.ForeignKey('studygroups.StudyGroup', on_delete=models.SET_NULL, null=True, blank=True)
      course = models.ForeignKey('studygroups.Course', on_delete=models.CASCADE)
      title = models.CharField(max_length=256)
      caption = models.CharField(max_length=512)
      link = models.URLField()
      image = models.ImageField(blank=True)
  
      def __str__(self):
          return self.title
  
subject: Add model changes