title: How to register inherited sub class in admin.py file in django?
body: <ul>
  <li>Project Name : fusion</li>
  <li>App Name : admin_lte </li>
  <li>Python 3.7 </li>
  <li>Django 2 </li>
  <li>MySql</li>
  </ul>
  
  <p>Question is "I want to register sub model in django admin-panel",when i write code for model registration in admin.py file that time occurred below error.</p>
  
  <blockquote>
    <p>django.core.exceptions.ImproperlyConfigured: The model Device is abstract, so it cannot be registered with admin.</p>
    
    <p><strong>NOTE : I used multiple separated model file.</strong></p>
  </blockquote>
  
  <p><strong>device.py (Model File)</strong></p>
  
  <pre><code>from django.db import models
  
  class Device(models.Model):
  device_type = models.CharField(max_length=100,blank=False)
  price = models.IntegerField()
  status =  models.CharField(max_length=10, default="SOLD")
  issues = models.CharField(max_length=100, default="No Issues")
  
  class Meta:
      abstract = True
  
  def __str__(self):
      return 'Device_type:{0} Price:{1}'.format(self.device_type,self.price)
  
  
  #Inheritance Concept
  class Laptop(Device):
     pass
     class Meta:
         db_table = "laptop"
  
  class Desktop(Device):
     pass
     class Meta:
         db_table = "Desktop"
  
  class Mobile(Device):
      pass
      class Meta:
          db_table = "Mobile"
  </code></pre>
  
  <hr>
  
  <p><strong>__init__.py File</strong></p>
  
  <pre><code>from django_adminlte.models.employee import Employee
  from django_adminlte.models.device import Device
  </code></pre>
  
  <hr>
  
  <p><strong>admin.py</strong></p>
  
  <pre><code>from django.contrib import admin
  from.models import Employee
  from.models import Device
  
  admin.site.register (Employee)
  admin.site.register (Device)
  </code></pre>
  
  <hr>
  
  <p>I want to show sub model (Desktop,Laptop,Mobile) in admin panel so admin can add some data from admin panel.</p>
  
  <hr>
  
  <p><a href="https://i.stack.imgur.com/jtoRz.jpg" rel="nofollow noreferrer">Project Structure Image :</a></p>