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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 delete_persistent_data(role, zk_node):
 """ Deletes any persistent data associated with the specified role, and zk node. :param role: the mesos role to delete, or None to omit this :type role: str :param zk_node: the zookeeper node to be deleted, or None to skip this deletion :type zk_node: str """

    if role:
        destroy_volumes(role)
        unreserve_resources(role)

    if zk_node:
        delete_zk_node(zk_node)