Compute datas produced for a many to one relationship

        :param obj obj: The instance we manage
        :param dict column: The column description dictionnary
        :returns: The associated value

def _get_to_one_relationship_value(self, obj, column):
        """
        Compute datas produced for a many to one relationship

        :param obj obj: The instance we manage
        :param dict column: The column description dictionnary
        :returns: The associated value
        """
        related_key = column.get('related_key', None)
        related = getattr(obj, column['__col__'].key)
        if related:
            if related_key is not None:
                value = self._get_formatted_val(
                    related, related_key, column
                )
            else:
                value = column['__prop__'].compile_obj(related)
        else:
            value = ""
        return value