public String getExpression() {
        return this.expression;
    }
<p>
A cluster query language expression to apply to the constraint. You cannot specify an expression if the
constraint type is <code>distinctInstance</code>. For more information, see <a
href="https://docs.aws.amazon.com/latest/developerguide/cluster-query-language.html">Cluster query language</a>
in the <i>Amazon ECS Developer Guide</i>.
</p>

@return A cluster query language expression to apply to the constraint. You cannot specify an expression if the
        constraint type is <code>distinctInstance</code>. For more information, see <a
        href="https://docs.aws.amazon.com/latest/developerguide/cluster-query-language.html">Cluster query
        language</a> in the <i>Amazon ECS Developer Guide</i>.
aws-java-sdk-scheduler/src/main/java/com/amazonaws/services/scheduler/model/PlacementConstraint.java