add comment & delete unused method
diff --git a/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/execution/operator/source/SeriesScanUtil.java b/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/execution/operator/source/SeriesScanUtil.java
index b115438..8176498 100644
--- a/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/execution/operator/source/SeriesScanUtil.java
+++ b/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/execution/operator/source/SeriesScanUtil.java
@@ -351,6 +351,7 @@
         }
       }
       initFirstChunkMetadata();
+      // filter chunk based on push-down conditions
       filterFirstChunkMetadata();
     }
     return Optional.of(firstChunkMetadata != null);
diff --git a/iotdb-core/datanode/src/test/java/org/apache/iotdb/db/storageengine/dataregion/read/reader/series/AbstractAlignedSeriesScanTest.java b/iotdb-core/datanode/src/test/java/org/apache/iotdb/db/storageengine/dataregion/read/reader/series/AbstractAlignedSeriesScanTest.java
index ba67112..74d5905 100644
--- a/iotdb-core/datanode/src/test/java/org/apache/iotdb/db/storageengine/dataregion/read/reader/series/AbstractAlignedSeriesScanTest.java
+++ b/iotdb-core/datanode/src/test/java/org/apache/iotdb/db/storageengine/dataregion/read/reader/series/AbstractAlignedSeriesScanTest.java
@@ -434,6 +434,4 @@
     BloomFilterCache.getInstance().clear();
     EnvironmentUtils.cleanAllDir();
   }
-
-  protected void assertWithOptionalReturnValue() {}
 }