def fetch(name, adapter_name = :default)
      adapter(adapter_name)[name] || adapter(:default)[name] ||
        raise(UnknownPluginError, name)
    end
def fetch(name, adapter_name = :default)
      adapter(adapter_name)[name] || adapter(:default)[name] ||
        raise(UnknownPluginError, name)
    end
Return the plugin for a given adapter

 @param [Symbol] name The name of the plugin
 @param [Symbol] adapter_name (:default) The name of the adapter used

 @raise [UnknownPluginError] if no plugin is found with the given name

 @api public