public boolean contains(Object o) {
            return TimelineHashMap.this.containsKey(o, epoch);
        }
This is a hash map which can be snapshotted.
<br>
See {@link SnapshottableHashTable} for more details about the implementation.
<br>
This class requires external synchronization.  Null keys and values are not supported.

@param <K>   The key type of the set.
@param <V>   The value type of the set.
server-common/src/main/java/org/apache/kafka/timeline/TimelineHashMap.java