code: func Register(name string, m Meddler) {
  	if name == "pk" {
  		panic("meddler.Register: pk cannot be used as a meddler name")
  	}
  	registry[name] = m
  }
docs: // Register sets up a meddler type. Meddlers get a chance to meddle with the
  // data being loaded or saved when a field is annotated with the name of the meddler.
  // The registry is global.