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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 __discoverPlugins():
 """ Discover the plugin classes contained in Python files, given a list of directory names to scan. Return a list of plugin classes. """

    for app in settings.INSTALLED_APPS:
        if not app.startswith('django'):
            module = __import__(app)
            moduledir = path.Path(module.__file__).parent
            plugin = moduledir / 'frog_plugin.py'
            if plugin.exists():
                file_, fpath, desc = imp.find_module('frog_plugin', [moduledir])
                if file_:
                    imp.load_module('frog_plugin', file_, fpath, desc)

    return FrogPluginRegistry.plugins