def getResourceFor(self, request):
        """
        Get a resource for a request.

        This iterates through the resource hierarchy, calling
        getChildWithDefault on each resource it finds for a path element,
        stopping when it hits an element where isLeaf is true.
        """
        request.site = self
        # Sitepath is used to determine cookie names between distributed
        # servers and disconnected sites.
        request.sitepath = copy.copy(request.prepath)
        return resource.getChildForRequest(self.resource, request)

        Get a resource for a request.

        This iterates through the resource hierarchy, calling
        getChildWithDefault on each resource it finds for a path element,
        stopping when it hits an element where isLeaf is true.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/server.py