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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 validate_proxy_granting_ticket(pgt, target_service):
 """ Validate a proxy granting ticket string. Return an ordered pair containing a ``ProxyTicket``, or a ``ValidationError`` if ticket validation failed. """

    logger.debug("Proxy ticket request received for %s using %s" % (target_service, pgt))

    pgt = ProxyGrantingTicket.objects.validate_ticket(pgt, target_service)
    pt = ProxyTicket.objects.create_ticket(service=target_service, user=pgt.user, granted_by_pgt=pgt)
    return pt