So let\'s say I have a webapp which just lets users save their hobbies. So I have Kind like this:
class Hobby(ndb.Model):
hobby_name = ndb.StringProperty()
<
I think you should look into Django packages for this type of behaviour.
This page from djangopackages.com references several packages doing exactly what you want, and written for Django. I suggest you have a look at django-autocomplete-light (the doc is great), or django-selectable, which is more similar to your question's approach.