Hi Dev,
Are you looking for example of how to use grouped model choice field in django. you can understand a concept of how to group the choices in a django select widget. Here you will learn django get choices from model. This post will give you simple example of django model choices from another model. Let's get started with how to get choice field value in django.
The Django provides forms API have two field types to work with multiple options: ChoiceField and ModelChoiceField.
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https://tuts-station.com/how-to-use-grouped-model-choice-field-in-django.html