The code adds WebSocket functionality for a Bitcoin blockchain explorer (Chronik), specifically the subscription and unsubscription to scripts:
Creates subscriptions to different script types (P2PKH, P2SH, P2PK, Other) with subscribe_to_script()
Verifies subscription status with assert_eq!(ep.subs.scripts, subscriptions)
Tests unsubscribing with unsubscribe_from_script()
Validates error handling for invalid/non-existent script subscriptions
Receives real-time notifications for transactions affecting subscribed scripts (mempool, confirmed, finalized events)