public boolean isEmpty() {
    return measurements == null || measurements.isEmpty();
  }
Updates this to be the difference of set between this and targetMeasurementSet. Returns the
intersection.

@param targetMeasurementSet The set to compare with measurement set of this.
@return A list of elements representing the intersection between measurement set of this and
    the targetMeasurementSet.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/schemaengine/template/alter/TemplateExtendInfo.java