@Override
  public List<Node> getChildren() {
    ImmutableList.Builder<Node> nodes = ImmutableList.builder();
    if (falseValue != null) {
      nodes.add(falseValue);
    }
    return nodes.add(condition).add(trueValue).build();
  }
IF(v1,v2[,v3]): CASE WHEN v1 THEN v2 [ELSE v3] END
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/sql/ast/IfExpression.java