code: def bulk_create_posts(self, posts, post_categories, post_tags, post_media_attachments):
          
          Post.objects.bulk_create(posts)
  
          # attach many-to-ones
          for post_wp_id, categories in six.iteritems(post_categories):
              Post.objects.get(site_id=self.site_id, wp_id=post_wp_id).categories.add(*categories)
  
          for post_id, tags in six.iteritems(post_tags):
              Post.objects.get(site_id=self.site_id, wp_id=post_id).tags.add(*tags)
  
          for post_id, attachments in six.iteritems(post_media_attachments):
              Post.objects.get(site_id=self.site_id, wp_id=post_id).attachments.add(*attachments)
docs: Actually do a db bulk creation of posts, and link up the many-to-many fields
  
          :param posts: the list of Post objects to bulk create
          :param post_categories: a mapping of Categories to add to newly created Posts
          :param post_tags: a mapping of Tags to add to newly created Posts
          :param post_media_attachments: a mapping of Medias to add to newly created Posts
          :return: None