docs: def locateChild(self, context, segments):
          """
          Delegate dispatch to a sharing resource if the request is for a user
          subdomain, otherwise fall back to the wrapped resource's C{locateChild}
          implementation.
          """
          request = IRequest(context)
          hostname = request.getHeader('host')
  
          info = self.subdomain(hostname)
          if info is not None:
              username, domain = info
              index = UserIndexPage(IRealm(self.siteStore),
                                    self.webViewer)
              resource = index.locateChild(None, [username])[0]
              return resource, segments
          return self.wrapped.locateChild(context, segments)