expose CometSchemaImporter in BatchReader

common/src/main/java/org/apache/comet/parquet/BatchReader.java

@@ -96,7 +96,7 @@
  */
 public class BatchReader extends RecordReader<Void, ColumnarBatch> implements Closeable {
   private static final Logger LOG = LoggerFactory.getLogger(FileReader.class);
-  protected static final BufferAllocator ALLOCATOR = new RootAllocator();
+  public static final BufferAllocator ALLOCATOR = new RootAllocator();
 
   private Configuration conf;
   private int capacity;
@@ -231,6 +231,10 @@ public BatchReader(AbstractColumnReader[] columnReaders) {
     this.taskContext = TaskContext$.MODULE$.get();
   }
 
+  public CometSchemaImporter getImporter() {
+    return importer;
+  }
+
   /**
    * Initialize this reader. The reason we don't do it in the constructor is that we want to close
    * any resource hold by this reader when error happens during the initialization.