Convert model to simple python structure.

def to_simple_model(self, instance, **options): # noqa
        """ Convert model to simple python structure.
        """
        options = self.init_options(**options)
        fields, include, exclude, related = options['fields'], options['include'], options['exclude'], options['related'] # noqa

        result = dict(
            model=smart_unicode(instance._meta),
            pk=smart_unicode(
                instance._get_pk_val(), strings_only=True),
            fields=dict(),
        )

        default_fields = set([field.name for field in instance._meta.fields if field.serialize])
        serialized_fields = fields or (default_fields | include) - exclude

        for fname in serialized_fields:

            # Respect `to_simple__<fname>`
            to_simple = getattr(
                self.scheme, 'to_simple__{0}'.format(fname), None)

            if to_simple:
                result['fields'][fname] = to_simple(instance, serializer=self)
                continue

            related_options = related.get(fname, dict())
            if related_options:
                related_options = self.init_options(**related_options)

            if fname in default_fields and not related_options:
                field = instance._meta.get_field(fname)
                value = field.value_from_object(instance)

            else:
                value = getattr(instance, fname, None)
                if isinstance(value, Manager):
                    value = value.all()

            result['fields'][fname] = self.to_simple(
                value, **related_options)

        if self.format != 'django':
            fields = result['fields']
            fields['id'] = result['pk']
            result = fields

        return result