app\models(14).py

#...

class User(db.Model, UserMixin):
    #...
    
    
    def is_following(self, user):
        if user.id is None:
            return False
        return self.followed.filter_by(
            followed_id=user.id).first() is not None

    def is_followed_by(self, user):
        if user.id is None:
            return False
        return self.followers.filter_by(
            follower_id=user.id).first() is not None
    
    def follow(self, user):
        client = stream.connect(current_app.config['STREAM_API_KEY'], current_app.config['STREAM_SECRET'])
        user_feed = client.feed("Notifications", str(self.id))
        if not self.is_following(user):
            user_feed.follow("User", str(user.id))
            f = Follow(follower=self, followed=user)
            db.session.add(f)
            return True

    def unfollow(self, user):
        client = stream.connect(current_app.config['STREAM_API_KEY'], current_app.config['STREAM_SECRET'])
        user_feed = client.feed("Notifications", str(self.id))
        f = self.followed.filter_by(followed_id=user.id).first()
        if f:
            user_feed.unfollow("User", str(user.id))
            db.session.delete(f)
            return True
    
    def is_following_collection(self, collection):
      if collection is None:
          return False
      if collection.id is None:
          return False
      return self.followed_collection.filter_by(
          collection_id=collection.id).first() is not None

    def follow_collection(self, collection):
      client = stream.connect(current_app.config['STREAM_API_KEY'], current_app.config['STREAM_SECRET'])
      user_feed = client.feed("Timeline", str(self.id))
      if not self.is_following_collection(collection):
          user_feed.follow("Collections", str(collection.id))
          f = CollectionFollow(c_follower=self, following=collection)
          db.session.add(f)
          return True

    def unfollow_collection(self, collection):
      client = stream.connect(current_app.config['STREAM_API_KEY'], current_app.config['STREAM_SECRET'])
      user_feed = client.feed("Timeline", str(self.id))
      f = self.followed_collection.filter_by(
          collection_id=collection.id).first()
      if f:
          user_feed.unfollow("Collections", str(collection.id))
          db.session.delete(f)
          return True
     #...