docs: 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