Django dynamic form attributes & clean methods

dynamic_form_attrs.py

import types
from django import forms

class DynamicAttrsForm(forms.ModelForm):

    class Meta:
        model = models.DynamicAttrs
        fields = ['template', 'mood', 'text' ]


    def __init__(self, *args, **kwargs):
        super(DynamicAttrsForm, self).__init__(*args, **kwargs)

        # This method generator must leave out of the for loop,
        # and must return an indirected function, else bad things
        # will happen. 
        def clean_sample_wrapper(sstype):

            def clean_sample_generic(self):
                sample = self.cleaned_data[sstype]
                if sample.mood != self.cleaned_data['mood']:
                    raise forms.ValidationError(
                        '%(sstype)s is not a sample of the selected mood!',
                        params={'sstype': sstype})

                return sample

            return clean_sample_generic

        for stid, stype in models.SAMPLE_TYPE_CHOICES.items():

            stype = unicode(stype).lower()
            sstype = str(stype)

            queryset = models.Sample.objects.filter(
                is_published=True, conv_status=1, type=stid
                ).order_by('name')

            if self.instance.pk:
                self.fields[sstype] = forms.ModelChoiceField(
                    label=stype, queryset=queryset,
                    initial=self.instance.sample_set.get(
                        sample__type=stid).sample.pk)

            else:
                self.fields[sstype] = forms.ModelChoiceField(
                    label=stype, queryset=queryset)

            setattr(self, 'clean_{0}'.format(stype),
                    types.MethodType(clean_sample_wrapper(sstype), self))