/// Registers interest in a transaction with `txid` and having an output with `script_pubkey` as
/// a spending condition.
fn register_tx(&self, txid: &Txid, script_pubkey: &Script);
/// Registers interest in a transaction with `txid` and having an output with `script_pubkey` as
/// a spending condition.
fn register_tx(&self, txid: &Txid, script_pubkey: &Script);