Added to admin docs how to add polymorphic child model as inline.

docs/admin.rst

@@ -53,6 +53,12 @@ use the ``base_form`` and ``base_fieldsets`` instead. The ``PolymorphicChildMode
 automatically detect the additional fields that the child model has, display those in a separate fieldset.
 
 
+Polymorphic Inlines
+-------------------
+
+To add a polymorphic child model as an Inline for another model, add a field to the inline's readonly_fields list formed by the lowercased name of the polymorphic parent model with the string "_ptr" appended to it. Otherwise, trying to save that model in the admin will raise an AttributeError with the message "can't set attribute".
+
+
 .. _admin-example:
 
 Example
@@ -64,7 +70,7 @@ The models are taken from :ref:`advanced-features`.
 
     from django.contrib import admin
     from polymorphic.admin import PolymorphicParentModelAdmin, PolymorphicChildModelAdmin
-    from .models import ModelA, ModelB, ModelC
+    from .models import ModelA, ModelB, ModelC, StandardModel
 
 
     class ModelAChildAdmin(PolymorphicChildModelAdmin):
@@ -78,9 +84,11 @@ The models are taken from :ref:`advanced-features`.
             ...
         )
 
+
     class ModelBAdmin(ModelAChildAdmin):
         # define custom features here
 
+
     class ModelCAdmin(ModelBAdmin):
         # define custom features here
 
@@ -93,5 +101,17 @@ The models are taken from :ref:`advanced-features`.
             (ModelC, ModelCAdmin),
         )
 
+
+	class ModelBInline(admin.StackedInline):
+	    model = ModelB
+	    fk_name = 'modelb'
+	    readonly_fields = ['modela_ptr']
+	
+		
+	class StandardModelAdmin(admin.ModelAdmin):
+		inlines = [ModelBInline]
+		
+
     # Only the parent needs to be registered:
     admin.site.register(ModelA, ModelAParentAdmin)
+    admin.site.register(StandardModel, StandardModelAdmin)