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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 get_plugin_class(self, plugin_name):
 """Returns the class registered under the given plugin name."""

        try:
            return self.plugin_classes[plugin_name]
        except KeyError:
            raise RezPluginError("Unrecognised %s plugin: '%s'"
                                 % (self.pretty_type_name, plugin_name))