ith additional methods
 to implement the additional semantics of that type of multipart
 content. The intent is that service providers, mail JavaBean writers
 and mail clients will write many such subclasses and their Command
 Beans, and will install them into the JavaBeans Activation
 Framework, so that any Jakarta Mail implementation and its clients can
 transparently find and use these classes. Thus, a MIME multipart
 handler is treated just like any other type handler, thereby
 decoupling the process of