transaction signals BIP125 replaceability or has an unconfirmed ancestor signaling BIP125 replaceability.
                                          
    "unbroadcast" : true|false            (boolean) Whether this transaction is currently unbroadcast (initial broadcast not yet acknowledged by any peers)
  },
  ...
}

Result (for verbose = false and mempool_sequence = true):
{                            (json object)
  "txids" : [                (json array)
    "hex",                   (string) The transact