old_contents: from django.db.models import ForeignKey, TextField
  
  from config import settings
  from yunity.base.models import BaseModel
  
  
  class Wall(BaseModel):
      pass
  
  
  class WallPost(BaseModel):
      wall = ForeignKey(Wall)
      author = ForeignKey(settings.AUTH_USER_MODEL)
  
  
  class WallPostContent(BaseModel):
      post = ForeignKey(WallPost)
      author = ForeignKey(settings.AUTH_USER_MODEL)
      body = TextField()
  
new_contents: from django.db.models import ForeignKey, TextField
  
  from config import settings
  from yunity.base.models import BaseModel
  
  
  class Wall(BaseModel):
      def resolve_permissions(self, collector):
          h = self.hub
          if h.target_content_type.model == 'group':
              g = h.target
              """:type : Group"""
              collector.add_hub(h, 'read')
              if g.is_content_included_in_parent:
                  g = g.parent
                  while g:
                      collector.add_hub(g.hub, 'read')
                      g = g.parent
  
  
  class WallPost(BaseModel):
      wall = ForeignKey(Wall)
      author = ForeignKey(settings.AUTH_USER_MODEL)
  
  
  class WallPostContent(BaseModel):
      post = ForeignKey(WallPost)
      author = ForeignKey(settings.AUTH_USER_MODEL)
      body = TextField()
  
subject: Implement basic permissions resolver for walls