@Override
    public H2DatabaseExtension withInitializer(DatabaseInitializer initializer) {
        if (this.initializerMaybe.isPresent()) {
            throw new IllegalStateException("Initializer already set!");
        }
        this.initializerMaybe = Optional.of(initializer);

        return this;
    }
Returns the last connection handed out by this extension. This is <b>not</b> a general
purpose API but is intended for tests that need to compare connection objects between a
handle and what the extension has handed out.
<br>
This API is <b>not multi-thread safe</b> and will not work if the extension is shared between
multiple threads.
@return A connection object. Can be null if no connection had been handed out.
core/src/test/java/org/jdbi/v3/core/junit5/H2DatabaseExtension.java