class Competition(models.Model):
    title = models.CharField(max_length=256)

class Gymnast(models.Model):
    parent = models.ForeignKey(Competition, related_name='gymnasts')
    name = models.CharField(max_length=256)

class Result(models.Model):
    parent = models.ForeignKey(Gymnast, related_name='results')

    score1 = models.FloatField(blank=True, null=True)
    score2 = models.FloatField(blank=True, null=True)
    score3 = models.FloatField(blank=True, null=True)
    score4 = models.FloatField(blank=True, null=True)
    score5 = models.FloatField(blank=True, null=True)
    score6 = models.FloatField(blank=True, null=True)
    score7 = models.FloatField(blank=True, null=True)

class YourModelForm(forms.ModelForm):

    extra_field = forms.CharField()

    def save(self, commit=True):
        extra_field = self.cleaned_data.get('extra_field', None)
        # ...do something with extra_field here...
        return super(YourModelForm, self).save(commit=commit)

    class Meta:
        model = YourModel

class PersonForm(forms.ModelForm):
    continent = forms.ChoiceField(choices=CONTINENT_CHOICES)

    class Meta:
        model = Person
        fields = ('__all__')
        widgets = {
            'birth_country': autocomplete.ModelSelect2(url='country-autocomplete',
                                                       forward=['continent'])
        }

class CountryAutocomplete(autocomplete.Select2QuerySetView):

    def get_queryset(self):
        if not self.request.user.is_authenticated():
            return Country.objects.none()

        qs = Country.objects.all()

        continent = self.forwarded.get('continent', None)

        if continent:
            qs = qs.filter(continent=continent)

        if self.q:
            qs = qs.filter(name__istartswith=self.q)

        return qs