public String getKey() {
        return this.key;
    }
<p>
One part of a key-value pair that defines a tag. The maximum length of a tag key is 128 characters. The minimum
length is 1 character.
</p>

@return One part of a key-value pair that defines a tag. The maximum length of a tag key is 128 characters. The
        minimum length is 1 character.
aws-java-sdk-pinpointemail/src/main/java/com/amazonaws/services/pinpointemail/model/Tag.java