Add the remove_document method to the Folder class

apps/folders/models.py

@@ -27,6 +27,10 @@ class Folder(models.Model):
     @property
     def documents(self):
         return [folder_document.document for folder_document in self.folderdocument_set.all()]
+        
+    def remove_document(self, document):
+        folder_document = self.folderdocument_set.get(document=document)
+        folder_document.delete()
 
     class Meta:
         unique_together = ('title', 'user')