code: def get_inline_instances(self, request, *args, **kwargs):
          
          inlines = super(PlaceholderEditorAdmin, self).get_inline_instances(request, *args, **kwargs)
  
          extra_inline_instances = []
          inlinetypes = self.get_extra_inlines()
          for InlineType in inlinetypes:
              inline_instance = InlineType(self.model, self.admin_site)
              extra_inline_instances.append(inline_instance)
  
          return extra_inline_instances + inlines
docs: Create the inlines for the admin, including the placeholder and contentitem inlines.