You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: event_log.rs
    path of file: ./repos/sled/src
    
    the code of the file until where you have to start completion: //! The `EventLog` lets us cheaply record and query behavior
//! in a concurrent system. It lets us reconstruct stories about
//! what happened to our data. It lets us write tests like:
//! 1. no keys are lost through tree structural modifications
//! 2. no nodes are made inaccessible through structural modifications
//! 3. no segments are zeroed and reused before all resident
//!    pages have been relocated and stabilized.
//! 4. recovery does not skip active segments
//! 5. no page is double-allocated or double-freed
//! 6. pages before restart match pages after restart
//!
//! What does it mean for data to be accessible?
//! 1. key -> page
//! 2. page -> lid
//! 3. lid ranges get stabiized over time
//! 4. lid ranges get zeroed over time
//! 5. segment trailers get written over time
//! 6. if a page's old location is zeroed 
    
    pub(crate) fn verify(&self) {
        let guard = pin();
        let iter = self.iter(&guard);

        // if we encounter a `PagesOnRecovery`, then we should
        // compare it to any subsequent `PagesOnShutdown`

        let mut recovered_pages = None;
        let mut recovered_meta = None;
        let mut minimum_lsn = None;

        for event in iter {
            match event {
                Event::Stabilized(lsn) | Event::RecoveredLsn(lsn) => {
                    if let Some(later_lsn) = minimum_lsn {
                        assert!(
                            later_lsn >= lsn,
                            "lsn must never go down between recoveries \
                            or stabilizations. It was {} but later became {}. history: {:?}",
                            lsn,
                            later_lsn,
                            self.iter(&guard)
                                .filter(|e| matches!(e, Event::Stabilized(_))
                                    || matches!(e, Event::RecoveredLsn(_)))
                                .collect::<Vec<_>>(),
                        );
                    }
                    minimum_lsn = Some(lsn);
                }
                Event::PagesOnRecovery { pages } => {
                    recovered_pages = Some(pages.clone());
                }
                Event::PagesOnShutdown { pages } => {
                    if let Some(ref par) = recovered_pages {
                        let pids = par
                            .iter()
                            .map(|(pid, _frag_locations)| *pid)
                            .chain(
                                pages.iter().map(|(pid, _frag_locations)| *pid),
                            )
                            .collect::<Set<_>>()
                            .into_iter();

                        for pid in pids {
                            // we filter out the blob pointer in the log
                            // because it is expected that upon recovery,
                            // any blob pointers will be forgotten from
                            // the log now that they are present in the
                            // snapshot.
                            let locations_before_restart: Vec<_> = pages
                                .get(&pid)
                                .unwrap()
                                .iter()
                                .map(|ptr_ref| {
                                    let mut ptr = *ptr_ref;
                                    ptr.forget_heap_log_coordinates();
                                    ptr
                                })
                                .collect();
                            let locations_after_restart: Vec<_> = par
                                .get(&pid)
                                .unwrap_or_else(|| panic!("pid {} no longer present after restart", pid))
                                .to_vec();
                            assert_eq!(
                                locations_before_restart,
                                locations_after_restart,
                                "page {} had frag locations {:?} before \
                                 restart, but {:?} after restart",
                                pid,
                                locations_before_restart,
                                locations_after_restart
                            );
                        }
                    }
                }
                Event::MetaOnRecovery { meta } => {
                    recovered_meta = Some(meta);
                }
                Event::MetaOnShutdown { meta } => {
                    if let Some(rec_meta) = recovered_meta {
                        assert_eq!(meta, rec_meta);
                    }
                }
            }
        }

        debug!("event log verified \u{2713}");
    }