@Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        PCollectionsImmutableSet<?> that = (PCollectionsImmutableSet<?>) o;
        return Objects.equals(underlying(), that.underlying());
    }
@param e the element
@return a wrapped hash-based persistent set that has a single element
@param <E> the element type
server-common/src/main/java/org/apache/kafka/server/immutable/pcollections/PCollectionsImmutableSet.java