default Generic add(Type upperBound) {
        getUpperBounds().add(upperBound);
        return this;
    }
Adds an upper bound to this generic.
<p>
In the following example, <code>List&lt;String&gt;</code> and
<code>Serializable</code> are upper bounds:
<pre>
    T extends List&lt;String&gt;&amp;Serializable
</pre>

@param upperBound the new upper bound
@return a reference to this model
common-parent/codegen/src/main/java/com/speedment/common/codegen/model/Generic.java