Added nullable annotation to method

Author: inv-jishnu

data-loader/core/src/main/java/com/scalar/db/dataloader/core/dataimport/task/ImportTask.java

@@ -31,6 +31,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
+import javax.annotation.Nullable;
 import lombok.RequiredArgsConstructor;
 
 /**
@@ -440,6 +441,7 @@ private boolean shouldFailForExistingData(
    * @param record the source record to include conditionally
    * @return the provided record if raw record logging is enabled; otherwise {@code null}
    */
+  @Nullable
   private ObjectNode getRecordForLogging(ObjectNode record) {
     return params.getImportOptions().isLogRawRecord() ? record : null;
   }