package io.burt.jmespath.ast;

public class FlattenListNode extends JmesPathNode {
  public FlattenListNode(JmesPathNode source) {
    super(source);
  }

  @Override
  protected boolean internalEquals(Object o) {
    return true;
  }

  @Override
  protected int internalHashCode() {
    return 19;
  }
}

package io.burt.jmespath.ast;

public class FlattenListNode extends JmesPathNode {
  public FlattenListNode() {
    super();
  }

  public FlattenListNode(JmesPathNode source) {
    super(source);
  }

  @Override
  protected boolean internalEquals(Object o) {
    return true;
  }

  @Override
  protected int internalHashCode() {
    return 19;
  }
}

--- 
+++ 
@@ -1,10 +1,6 @@
 package io.burt.jmespath.ast;
 
 public class FlattenListNode extends JmesPathNode {
-  public FlattenListNode() {
-    super();
-  }
-
   public FlattenListNode(JmesPathNode source) {
     super(source);
   }
Remove the no-args constructor from FlattenNode

It is not used.