code: func WrapRegistererWith(labels Labels, reg Registerer) Registerer {
  	return &wrappingRegisterer{
  		wrappedRegisterer: reg,
  		labels:            labels,
  	}
  }
docs: // WrapRegistererWith returns a Registerer wrapping the provided
  // Registerer. Collectors registered with the returned Registerer will be
  // registered with the wrapped Registerer in a modified way. The modified
  // Collector adds the provided Labels to all Metrics it collects (as
  // ConstLabels). The Metrics collected by the unmodified Collector must not
  // duplicate any of those labels.
  //
  // WrapRegistererWith provides a way to add fixed labels to a subset of
  // Collectors. It should not be used to add fixed labels to all metrics exposed.
  //
  // The Collector example demonstrates a use of WrapRegistererWith.