code: private Map<String, List<PortBinding>> portBindings() {
      final Map<String, List<PortBinding>> bindings = Maps.newHashMap();
      for (final Map.Entry<String, PortMapping> e : job.getPorts().entrySet()) {
        final PortMapping mapping = e.getValue();
        final Integer jobDefinedExtPort = mapping.getExternalPort();
  
        // If the job didn't specify an external port, use dynamically allocated ports
        final String externalPort = jobDefinedExtPort == null
                                    ? ports.get(e.getKey()).toString() : jobDefinedExtPort.toString();
  
        final PortBinding binding = PortBinding.of(mapping.getIp(), externalPort);
        final String entry = containerPort(mapping.getInternalPort(), mapping.getProtocol());
        bindings.put(entry, Collections.singletonList(binding));
      }
      return bindings;
    }
docs: Create a port binding configuration for the job.
  
  @return The port bindings.