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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 configure(cls, name, config, prefix='depot.'):
 """Configures an application depot. This configures the application wide depot from a settings dictionary. The settings dictionary is usually loaded from an application configuration file where all the depot options are specified with a given ``prefix``. The default ``prefix`` is *depot.*, the minimum required setting is ``depot.backend`` which specified the required backend for files storage. Additional options depend on the choosen backend. """

        if name in cls._depots:
            raise RuntimeError('Depot %s has already been configured' % (name,))

        if cls._default_depot is None:
            cls._default_depot = name

        cls._depots[name] = cls.from_config(config, prefix)
        return cls._depots[name]