public Tag withKey(String key) {
        setKey(key);
        return this;
    }
<p>
<i>Required</i>. A string used to identify this tag. You can specify a maximum of 128 characters for a tag key.
Tags owned by Amazon Web Services (Amazon Web Services) have the reserved prefix: <code>aws:</code>.
</p>

@param key
       <i>Required</i>. A string used to identify this tag. You can specify a maximum of 128 characters for a tag
       key. Tags owned by Amazon Web Services (Amazon Web Services) have the reserved prefix: <code>aws:</code>.
@return Returns a reference to this object so that method calls can be chained together.
aws-java-sdk-cloudformation/src/main/java/com/amazonaws/services/cloudformation/model/Tag.java