code: func (conf FilterConfigurator) apply(f func([]Filter) []Filter) {
  	// Updates any actions that have had their filters overridden, if this is a
  	// Controller configurator.
  	if conf.controllerName == conf.key {
  		for k, v := range filterOverrides {
  			if strings.HasPrefix(k, conf.controllerName+".") {
  				filterOverrides[k] = f(v)
  			}
  		}
  	}
  
  	// Update the Controller or Action overrides.
  	filterOverrides[conf.key] = f(conf.getChain())
  }
docs: // apply applies the given functional change to the filter overrides.
  // No other function modifies the filterOverrides map.