A token that contains a javax.media.Buffer. This token is used when
dealing with images in the Java Media Framework (JMF) library. Because
it extends ImageToken, it can be used with the standard image processing
tools by simply casting it, and calling asAWTImage().
Return a description of the token.
If possible, derived classes should override this method and
return the value of this token as a string that can be parsed
by the expression language to recover a token with the same value.
Unfortunately, in this base class, we can only return the
a partial description of the token.