           (numeric) transaction fee, denominated in BTC
      "modified" : n,                     (numeric) transaction fee with fee deltas used for mining priority, denominated in BTC
      "ancestor" : n,                     (numeric) transaction fees of in-mempool ancestors (including this one) with fee deltas used for mining priority, denominated in BTC
      "descendant" : n                    (numeric) transaction fees of in-mempool descendants (including this one) with fee deltas used for mining pri