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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def load_classes(cls, fail_silently=True):
 """Load all the classes for a plugin. Produces a sequence containing the identifiers and their corresponding classes for all of the available instances of this plugin. fail_silently causes the code to simply log warnings if a plugin cannot import. The goal is to be able to use part of libraries from an XBlock (and thus have it installed), even if the overall XBlock cannot be used (e.g. depends on Django in a non-Django application). There is disagreement about whether this is a good idea, or whether we should see failures early (e.g. on startup or first page load), and in what contexts. Hence, the flag. """

        all_classes = itertools.chain(
            pkg_resources.iter_entry_points(cls.entry_point),
            (entry_point for identifier, entry_point in cls.extra_entry_points),
        )
        for class_ in all_classes:
            try:
                yield (class_.name, cls._load_class_entry_point(class_))
            except Exception:  # pylint: disable=broad-except
                if fail_silently:
                    log.warning('Unable to load %s %r', cls.__name__, class_.name, exc_info=True)
                else:
                    raise