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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 aname(cls, map_name, attached_name, parent_name=None):
 """ Generates a container name that should be used for creating new attached volume containers and checking the status of existing containers. In this implementation, the format will be ``<map name>.<attached>``, or ``<map name>.<parent name>.<attached>`` if the parent container configuration name is provided. :param map_name: Container map name. :type map_name: unicode | str :param attached_name: Attached container alias. :type attached_name: unicode | str :param parent_name: Container configuration name that has contains attached container. :type parent_name: unicode | str :return: Container name. :rtype: unicode | str """

        if parent_name:
            return '{0}.{1}.{2}'.format(map_name, parent_name, attached_name)
        return '{0}.{1}'.format(map_name, attached_name)