code: public Traverson startWith(final URL contextUrl, final HalRepresentation resource) {
          this.startWith = null;
          this.contextUrl = requireNonNull(contextUrl);
          this.lastResult = singletonList(requireNonNull(resource));
          return this;
      }
docs: Start traversal at the given HAL resource, using the {@code contextUrl} to resolve relative links.
  
  <p>
  If the {@code resource} is obtained from another Traverson, {@link Traverson#getCurrentContextUrl()}
  can be called to get this URL.
  </p>
  
  @param contextUrl URL of the Traverson's current context, used to resolve relative links
  @param resource the initial HAL resource.
  @return Traverson initialized with the specified {@link HalRepresentation} and {@code contextUrl}.
  @since 1.0.0