+ "View MESSAGE in MIME-View mode.
+
+Optional argument PREVIEW-BUFFER specifies the buffer of the
+presentation. It must be either nil or a name of preview buffer.
+
+Optional argument MOTHER specifies mother-buffer of the preview-buffer.
+
+Optional argument DEFAULT-KEYMAP-OR-FUNCTION is nil, keymap or
+function. If it is a keymap, keymap of MIME-View mode will be added
+to it. If it is a function, it will be bound as default binding of
+keymap of MIME-View mode."