agent/metrics/metrics_engine.go
func MustInit(cfg *config.Config, registry ...*prometheus.Registry) {
	if !cfg.PrometheusMetricsEnabled {
		return
	}
	var registryToUse *prometheus.Registry
	if len(registry) > 0 {
		registryToUse = registry[0]
	} else {
		registryToUse = prometheus.DefaultRegisterer.(*prometheus.Registry)
	}
	MetricsEngineGlobal = NewMetricsEngine(cfg, registryToUse)
	MetricsEngineGlobal.collection = true
}
func MustInit(cfg *config.Config, registry ...*prometheus.Registry) {
	if !cfg.PrometheusMetricsEnabled {
		return
	}
	var registryToUse *prometheus.Registry
	if len(registry) > 0 {
		registryToUse = registry[0]
	} else {
		registryToUse = prometheus.DefaultRegisterer.(*prometheus.Registry)
	}
	MetricsEngineGlobal = NewMetricsEngine(cfg, registryToUse)
	MetricsEngineGlobal.collection = true
}
// Initializes the Global MetricsEngine used throughout Agent
// Currently, we use the Prometheus Global Default Registerer, which also collecs
// basic Go application metrics that we use (like memory usage).
// In future cases, we can use a custom Prometheus Registry to group metrics.
// For unit testing purposes, we only focus on API calls and use our own Registry