added get_absolute_url method in Books class

bellapanghulan_reading/bookshelf/models.py

 from datetime import datetime
 from django.db import models
+from django.urls import reverse
 from django.core.exceptions import ValidationError
 
 # Create your models here.
@@ -39,6 +40,8 @@ class Books(models.Model):
     ISBN = models.CharField(max_length=13, validators=[validate_ISBN])
     blurb = models.TextField(validators=[validate_wordCount])
     
-    
     def __str__(self):
         return self.title
+    
+    def get_absolute_url(self):
+        return reverse('book-details', kwargs={'pk': self.pk})