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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 atlas_peer_set_zonefile_inventory( peer_hostport, peer_inv, peer_table=None ):
 """ Set this peer's zonefile inventory """

    with AtlasPeerTableLocked(peer_table) as ptbl:
        if peer_hostport not in ptbl.keys():
            return None 

        ptbl[peer_hostport]['zonefile_inv'] = peer_inv

    return peer_inv