'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.'

def _convert_many_to_one(self, col_name, label, description, lst_validators, filter_rel_fields, form_props):

    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
