Customize options inside the ModelChoiceField Django forms

I have a django form like this:

class AddUserGroupFrom(forms.ModelForm):
    class Meta:
        model = UsersGroups
        fields = (
            'tag',
        )
        widgets = {
            'tag': forms.TextInput(attrs={'class': 'form-control', 'placeholder': 'Work, home, etc..'}),
        }
    
    def __init__(self, *args, **kwargs):
        super(AddUserGroupFrom, self).__init__(*args, **kwargs)
        self.fields['city'] = forms.ModelChoiceField(
            queryset=Group.objects.values_list('city').all().distinct(),
            widget=forms.Select(attrs={
                'class': 'form-select form-select-sm mb-3',
                'aria-label': '.form-select-sm example',
            }),
            label='Choose city name',
            empty_label='Select city',
        )
        self.fields['group'] = forms.ModelChoiceField(
            queryset=Group.objects.values_list('group_number').all(),
            widget=forms.Select(attrs={
                'class': 'form-select form-select-sm mb-3',
                'aria-label': '.form-select-sm example',
            }),
            label='Choose group number',
            empty_label='Select group',
        )

The problem that in my select field options displayed as tuples
Form representation
Templates look like this:

<form action="" method="post">
        {% csrf_token %}

        <div class="mb-3">
            <label for="{{ add_group_form.tag.id_for_label }}" class="form-label">{{ add_group_form.tag.label }}</label>
            {{ add_group_form.tag }}
        </div>

        <label for="{{ add_group_form.city.id_for_label }}">{{ add_group_form.city.label }}</label>
        {{ add_group_form.city }}

        <label for="{{ add_group_form.group.id_for_label }}">{{ add_group_form.group.label }}</label>
        {{ add_group_form.group }}

        <input type="submit" value="Save changes" class="btn btn-success">
    </form>

How can I remove tuple-style representation in options inside the select field?

I tried to iterate within indexes in templates:
{{ add_group_form.city[0] }}
But it throws error:

> Could not parse the remainder: '[0]' from 'add_group_form.city[0]'

You can create a tuple with the city values and assign it to the choices of the form field. Normally you do not define the form fields in the init method. It looks like city is not a model field. That's why I changed it to a ChocieField.
(code is not tested, change it if needed)

class AddUserGroupFrom(forms.ModelForm):
    city = forms.ChoiceField(
        choices=[],
        empty_label='Select city',
        label='Choose city name',
        widget=forms.Select(attrs={
            'class': 'form-select form-select-sm mb-3',
            'aria-label': '.form-select-sm example',
        }),
    )

    group = forms.ModelChoiceField(
        queryset=Group.objects.all(),
        empty_label='Select group',
        label='Choose group number',
        widget=forms.Select(attrs={
            'class': 'form-select form-select-sm mb-3',
            'aria-label': '.form-select-sm example',
        }),
    )

    class Meta:
        model = UsersGroups
        fields = ('tag',)
        widgets = {
            'tag': forms.TextInput(attrs={'class': 'form-control', 'placeholder': 'Work, home, etc..'}),
        }
    
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        city_list = Group.objects.values_list('city', flat=True)
        city_choices = [(city, city) for city in city_list]
        self.fields['city'].choices = city_choices