@SuppressWarnings("unchecked")
    default T add(final Type interf) {
        getInterfaces().add(interf);
        return (T) this;
    }
Adds the specified interface to the list of implemented interfaces of
this model. The type should represent an interface.

@param interf  the implemented interface
@return        a reference to this
common-parent/codegen/src/main/java/com/speedment/common/codegen/model/trait/HasImplements.java