public Tag withKey(String key) {
        setKey(key);
        return this;
    }
<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>

@param key
       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.
@return Returns a reference to this object so that method calls can be chained together.
aws-java-sdk-pinpointemail/src/main/java/com/amazonaws/services/pinpointemail/model/Tag.java