-/// let mut listeners = vec![];
-/// if let Some(monitor_block_hash) = monitor_block_hash_option {
-/// listeners.push((monitor_block_hash, &mut monitor_listener as &mut dyn chain::Listen))
-/// }
-/// if let Some(manager_block_hash) = manager_block_hash_option {
-/// listeners.push((manager_block_hash, &mut manager as &mut dyn chain::Listen))
-/// }
+/// let listeners = vec![
+/// (monitor_block_hash, &monitor_listener as &dyn chain::Listen),
+/// (manager_block_hash, &manager as &dyn chain::Listen),
+/// ];