Cleaning code

bookshelf/models.py

 from django.db import models
-from django.core.validators import MaxValueValidator, MinValueValidator 
+from django.core.validators import MaxValueValidator, MinValueValidator
 from django.urls import reverse
 
+
 class Author(models.Model):
     first_name = models.CharField(max_length=50)
     last_name = models.CharField(max_length=50)
@@ -15,7 +16,8 @@ class Author(models.Model):
 
 class Books(models.Model):
     title = models.CharField(max_length=200)
-    author = models.ForeignKey(Author, related_name="books", on_delete=models.CASCADE)
+    author = models.ForeignKey(Author, related_name="books",
+                               on_delete=models.CASCADE)
     publisher = models.CharField(max_length=200)
     year_published = models.DateField()
     ISBN = models.PositiveIntegerField(

bookshelf/urls.py

 
 from django.urls import path
 from . import views
-from .views import (HomeView, BooksListView, BooksDetailView, 
+from .views import (HomeView, BooksListView, BooksDetailView,
                     AuthorListView, AuthorDetailView)
 
 
 urlpatterns = [
     path('home/', views.HomeView, name='home'),
     path('books/', BooksListView.as_view(), name='books'),
-    path('books/<int:pk>/details', BooksDetailView.as_view(), 
+    path('books/<int:pk>/details', BooksDetailView.as_view(),
          name='books-detail'),
     path('authors/', AuthorListView.as_view(), name='author'),
-    path('authors/<int:pk>/details', AuthorDetailView.as_view(), 
+    path('authors/<int:pk>/details', AuthorDetailView.as_view(),
          name='author-detail'),
 
 ]

bookshelf/views.py

 from django.shortcuts import render
-from django.http import HttpResponse
 from django.views.generic.detail import DetailView
 from django.views.generic.list import ListView
-from django.views import View
 from .models import Books
 from .models import Author
-from django.views import generic
 
 
 def HomeView(request):