text: import os
  from prometheus_client import generate_latest, CONTENT_TYPE_LATEST, REGISTRY, multiprocess, CollectorRegistry
  from starlette.responses import Response
  
  from .middleware import PrometheusMiddleware
  
  def handle_metrics(request):
      """ A handler to expose Prometheus metrics
          Example usage:
  
          ```
          app.add_middleware(PrometheusMiddleware)
          app.add_route("/metrics", handle_metrics)
          ```
      """
      registry = REGISTRY
      if 'prometheus_multiproc_dir' in os.environ:
          registry = CollectorRegistry()
          multiprocess.MultiProcessCollector(registry)
      
      headers = {'Content-Type': CONTENT_TYPE_LATEST}
      return Response(generate_latest(), status_code=200, headers=headers)
  