Reguster plugins. The plugins parameter should be dict mapping model to plugin.

        Just calls a register_plugin for every such a pair.

def register_plugins(cls, plugins):
        '''
        Reguster plugins. The plugins parameter should be dict mapping model to plugin.

        Just calls a register_plugin for every such a pair.
        '''
        for model in plugins:
            cls.register_plugin(model, plugins[model])