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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _convert_many_to_one(self, col_name, label, description, lst_validators, filter_rel_fields, form_props):
 """ Creates a WTForm field for many to one related fields, will use a Select box based on a query. Will only work with SQLAlchemy interface. """

        query_func = self._get_related_query_func(col_name, filter_rel_fields)
        get_pk_func = self._get_related_pk_func(col_name)
        extra_classes = None
        allow_blank = True
        if not self.datamodel.is_nullable(col_name):
            lst_validators.append(validators.DataRequired())
            allow_blank = False
        else:
            lst_validators.append(validators.Optional())
        form_props[col_name] = \
            QuerySelectField(label,
                             description=description,
                             query_func=query_func,
                             get_pk_func=get_pk_func,
                             allow_blank=allow_blank,
                             validators=lst_validators,
                             widget=Select2Widget(extra_classes=extra_classes))
        return form_props