@Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        } else if (!(o instanceof FlattenExpression)) {
            return false;
        }
        FlattenExpression that = (FlattenExpression) o;
        return expression.equals(that.expression);
    }
Returns the expression being flattened.

@return Returns the expression.
smithy-jmespath/src/main/java/software/amazon/smithy/jmespath/ast/FlattenExpression.java