fixed the foreignkey

bookshelf/models.py

+from django.db import models
+# -- coding: UTF-8 --
+
+
+class Author(models.Model):
+    first_name = models.CharField(max_length=50)
+    last_name = models.CharField(max_length=50)
+    age = models.IntegerField()
+    nationality = models.CharField(max_length=50)
+    bio = models.CharField(max_length=700)
+
+
+class Books(models.Model):
+    title = models.CharField(max_length=125)
+    author = models.ForeignKey(Author, on_delete=models.CASCADE)
+    publisher = models.CharField(max_length=100)
+    year_published = models.IntegerField(max_length=100)
+    isbn = models.CharField(max_length=13)
+    blurb = models.TextField()