Save images with generic foreign key

python

import os
import datetime
from django.db import models
from django.contrib.contenttypes.fields import GenericForeignKey
from django.contrib.contenttypes.models import ContentType


def get_upload_path(instance, filename):
    name = instance.__class__.__name__.lower()
    return os.path.join('{}_{}_{}/{}/{}'.format(
        datetime.datetime.now().day,
        datetime.datetime.now().month,
        datetime.datetime.now().year, name, filename))


class ContentManager(models.Manager):
    def all(self):
        qs = super().all()
        return qs

    def filter_by_instance(self, instance):
        content_type = ContentType.objects.get_for_model(instance.__class__)
        obj_id = instance.id
        qs = super().filter(
            content_type=content_type, object_id=obj_id)
        return qs


class Media(models.Model):
    image = models.ImageField(upload_to=get_upload_path)
    caption = models.CharField(blank=True, max_length=255)
    content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
    object_id = models.PositiveIntegerField()
    content_object = GenericForeignKey('content_type', 'object_id')
    created_date = models.DateTimeField(auto_now_add=True)
    modified_date = models.DateTimeField(auto_now=True)
    is_published = models.BooleanField(default=False)
    order = models.PositiveSmallIntegerField(
            default=0, blank=False, null=False)

    objects = ContentManager()

    class Meta:
        default_related_name = 'media'
        verbose_name = 'media'
        verbose_name_plural = 'media'
        ordering = ['order']

    def get_object(self):
        ct = ContentType.objects.get_for_model(self.content_object)
        obj = ct.get_object_for_this_type(pk=self.object_id)
        return obj

    def filename(self):
        return os.path.basename(self.image.name)

    def __str__(self):
        return self.filename()