public void setKey(String key) {
        this.key = key;
    }
<p>
Part of the key:value pair that defines a tag. You can use a tag key to describe a category of information, such
as "customer." Tag keys are case-sensitive.
</p>

@param key
       Part of the key:value pair that defines a tag. You can use a tag key to describe a category of
       information, such as "customer." Tag keys are case-sensitive.
aws-java-sdk-fms/src/main/java/com/amazonaws/services/fms/model/Tag.java