Returns the attribute (specified by its representation name) from
        the map of all mapped attributes for the given mapped class and
        attribute key. See :method:`get_attribute_map` for details.

def get_attribute_by_repr(self, attribute_repr_name, mapped_class=None,
                              key=None):
        """
        Returns the attribute (specified by its representation name) from
        the map of all mapped attributes for the given mapped class and
        attribute key. See :method:`get_attribute_map` for details.
        """
        attr_map = self.__get_attribute_map(mapped_class, key, 1)
        try:
            return attr_map[attribute_repr_name]
        except KeyError:
            raise AttributeError(attribute_repr_name)