@Override
  public final String toString() {
    String outputSymbol = getOutputSymbol();
    String expressionString = getExpressionString();
    if (!Objects.equals(outputSymbol, expressionString)) {
      return expressionString + " [" + outputSymbol + "]";
    }
    return expressionString;
  }
This method is only displayed during debugging, please use {@link #getExpressionString()} or
{@link #getOutputSymbol()} in the code.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/expression/Expression.java