code: func (p *Namespaces) List() (out []Namespace) {
  	if !p.Safe {
  		p.mu.RLock()
  		defer p.mu.RUnlock()
  	}
  	out = make([]Namespace, 0, len(p.prefixes))
  	for pref, ns := range p.prefixes {
  		out = append(out, Namespace{Prefix: pref, Full: ns})
  	}
  	return
  }
docs: // List enumerates all registered namespace pairs.