public static Builder builder() {
    return new Builder();
  }
@Test
  @SuppressWarnings("JdkObsolete") // for hashtable
  public void testBuilder_environmentMapTypes() {
    // Can accept empty environment.
    Assert.assertNotNull(
        ContainerConfiguration.builder().setEnvironment(ImmutableMap.of()).build());
    // Can handle other map types (https://github.com/GoogleContainerTools/jib/issues/632)
    Assert.assertNotNull(ContainerConfiguration.builder().setEnvironment(new TreeMap<>()));
    Assert.assertNotNull(ContainerConfiguration.builder().setEnvironment(new Hashtable<>()));
  }