public void cleanup() {
            final ExecSessionInternal exec = newExecSessionInternal(this.resumeState.getExecSessionConfigSource());
            bulkLoader.cleanup(exec, config, resumeState);
        }
Sets an alternative {@code BulkLoader} instance mainly for testing-purpose.
embulk-core/src/main/java/org/embulk/EmbulkEmbed.java