'Scan library_books for any paths not on device
Remove any iTunes orphans originally added by calibre
This occurs when the user deletes a book in iBooks while disconnected'

def _purge_orphans(self, library_books, cached_books):

    PURGE_ORPHANS = False
    if self.verbose:
        logger().info(('    %s._purge_orphans()' % self.__class__.__name__))
    for book in library_books:
        if isosx:
            if ((book not in cached_books) and str(library_books[book].description()).startswith(self.description_prefix)):
                if PURGE_ORPHANS:
                    if self.verbose:
                        logger().info(("        '%s'    not    found    on    iDevice,    removing    from    iTunes" % book))
                    btr = {'title': library_books[book].name(), 'author': library_books[book].artist(), 'lib_book': library_books[book]}
                    self._remove_from_iTunes(btr)
                elif self.verbose:
                    logger().info(("        '%s'    found    in    iTunes,    but    not    on    iDevice" % book))
        elif iswindows:
            if ((book not in cached_books) and library_books[book].Description.startswith(self.description_prefix)):
                if PURGE_ORPHANS:
                    if self.verbose:
                        logger().info(("        '%s'    not    found    on    iDevice,    removing    from    iTunes" % book))
                    btr = {'title': library_books[book].Name, 'author': library_books[book].Artist, 'lib_book': library_books[book]}
                    self._remove_from_iTunes(btr)
                elif self.verbose:
                    logger().info(("        '%s'    found    in    iTunes,    but    not    on    iDevice" % book))
