$index->setSettings([
  'renderingContent' => [
    'facetOrdering' => [
      'facets' => [
        'order' => [ 'gender', 'size', 'price' ]
      ]
    ]
  ]
]);

index.set_settings({
  renderingContent: {
    facetOrdering: {
      facets: {
        order: [ 'gender', 'size', 'price' ]
      }
    }
  }
})

index.set_settings({
  'renderingContent': {
    facetOrdering: {
      facets: {
        order: [ 'gender', 'size', 'price' ],
      },
    },
  },
})