code: func NewMetricsEngine(cfg *config.Config, registry *prometheus.Registry) *MetricsEngine {
  	metricsEngine := &MetricsEngine{
  		cfg:            cfg,
  		Registry:       registry,
  		managedMetrics: make(map[APIType]MetricsClient),
  	}
  	for managedAPI, _ := range managedAPIs {
  		aClient := NewMetricsClient(managedAPI, metricsEngine.Registry)
  		metricsEngine.managedMetrics[managedAPI] = aClient
  	}
  	return metricsEngine
  }
docs: // We create a MetricsClient for all managed APIs (APIs for which we will collect
  // metrics)