or string, optional, default=not set, fall back to wallet fee estimation) Specify a fee rate in sat/vB.
5. options                     (json object, optional) Options object that can be used to pass named arguments, listed below.

Named Arguments:
add_to_wallet              (boolean, optional, default=true) When false, returns the serialized transaction without broadcasting or adding it to the wallet
fee_rate                   (numeric or string, optional, default=not set, fall back to wallet fee estimation