在django中从父类中的对象查找子类中的对象

Let's say I have a parent class (ThingsThatMigrate) and two children (Coconut and Swallow). Now let's say I have a ThingsThatMigrate object. How can I determine if it is in fact a Coconut or a Swallow? Once having done so, how can I get to the Coconut or Swallow object?Let's say I have a parent class (ThingsThatMigr