public void setKey(String key) {
        this.key = key;
    }
<p>
Can be either <code>tag:</code> <i>tag-key</i> or <code>InstanceIds</code>.
</p>

@param key
       Can be either <code>tag:</code> <i>tag-key</i> or <code>InstanceIds</code>.
aws-java-sdk-eventbridge/src/main/java/com/amazonaws/services/eventbridge/model/RunCommandTarget.java