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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 set_default_loader(loader):
 """ Set defaulr loader instance Parameters loader : instance or string An instance or registered name of loader class. The specified loader instance will be used when user did not specified :attr:`loader` in :func:`maidenhair.functions.load` function. See also -------- :func:`maidenhair.utils.plugins.Registry.register` : Register new class """

    if isinstance(loader, basestring):
        loader = registry.find(loader)()
    if not isinstance(loader, BaseLoader):
        loader = loader()
    global _loader
    _loader = loader