DynamicChoiceField for Django REST Framework 3.x

fields.py

class DynamicChoiceField(ChoiceField):
    """ Privides set_choices method used to update all choice related attributes of the field """
    def set_choices(self, choices):
        """ Unfortunately just setting field.choices is not enough so we will sue this class to update evverything """

        self.grouped_choices = to_choices_dict(choices)
        self.choices = flatten_choices_dict(self.grouped_choices)

        self.choice_strings_to_values = dict([
            (six.text_type(key), key) for key in self.choices.keys()
        ])