Trecho do forms.py

forms.py

class ContatoAgrupadoPorGrupoFilterSet(FilterSet):
    search = MethodFilter()

    municipio = MethodModelChoiceFilter(
        required=False,
        queryset=Municipio.objects.all())

    grupo = MethodModelChoiceFilter(
        required=False,
        queryset=GrupoDeContatos.objects.all())

    def filter_municipio(self, queryset, value):
        import pdb; pdb.set_trace()

        queryset = queryset.filter(nome=value)
        return queryset

    def filter_grupo(self, queryset, value):
        queryset = queryset.filter(nome=value)
        return queryset

    class Meta:
        model = Contato
        fields = ['municipio', ]

    def __init__(self, data=None,
                 queryset=None, prefix=None, strict=None, **kwargs):

        workspace = kwargs.pop('workspace')

        super(ContatoAgrupadoPorGrupoFilterSet, self).__init__(
            data=data,
            queryset=queryset, prefix=prefix, strict=strict, **kwargs)

        c1_row1 = to_row([
            ('municipio', 7),
            ('grupo', 7),
        ])

        col1 = Fieldset(
            _('Informações para Seleção de Contados'),
            c1_row1,
            to_row([
                (SubmitFilterPrint(
                    'filter',
                    value=_('Filtrar'),
                    css_class='btn-default pull-right',
                    type='submit'), 12)
            ]))

        col2 = Fieldset(
            _('Inf p/ Impressão'),

            SubmitFilterPrint(
                'print',
                value=_('Imprimir'),
                css_class='btn-primary pull-right',
                type='submit')
        )

        rows = to_row([
            (col1, 9),
            (col2, 3),
        ])

        self.form.helper = FormHelper()
        self.form.helper.form_method = 'GET'
        self.form.helper.layout = Layout(
            rows,
        )

        self.form.fields['grupo'].queryset = GrupoDeContatos.objects.filter(
            workspace=workspace)
        self.form.fields['municipio'].queryset = Municipio.objects.all()