ngs)
  "transactionid"           (string) The transaction id of an in-mempool descendant transaction
  ,...
]

Result (for verbose = true):
{                           (json object)
  "transactionid" : {       (json object)
    "size" : n,             (numeric) virtual transaction size as defined in BIP 141. This is different from actual serialized size for witness transactions as witness data is discounted.
    "fee" : n,              (numeric) transaction fee in BTC (DEPRECATED)
    "modifiedfee" : n,    