message: More std::optional
diff: @@ -259,7 +259,7 @@ PYBIND11_MODULE(eos, eos_module)
  const core::LandmarkMapper& landmark_mapper, int image_width, int image_height,
  const morphablemodel::EdgeTopology& edge_topology,
  const fitting::ContourLandmarks& contour_landmarks, const fitting::ModelContour& model_contour,
  - int num_iterations, std::optional<int> num_shape_coefficients_to_fit, float lambda) {
  + int num_iterations, cpp17::optional<int> num_shape_coefficients_to_fit, float lambda) {
  assert(landmarks.size() == landmark_ids.size());
  std::vector<float> pca_coeffs;
  std::vector<float> blendshape_coeffs;
  @@ -269,7 +269,7 @@ PYBIND11_MODULE(eos, eos_module)
  {
  landmark_collection.push_back(core::Landmark<Eigen::Vector2f>{ landmark_ids[i], Eigen::Vector2f(landmarks[i][0], landmarks[i][1]) });
  }
  - auto result = fitting::fit_shape_and_pose(morphable_model, blendshapes, landmark_collection, landmark_mapper, image_width, image_height, edge_topology, contour_landmarks, model_contour, num_iterations, num_shape_coefficients_to_fit, lambda, std::nullopt, pca_coeffs, blendshape_coeffs, fitted_image_points);
  + auto result = fitting::fit_shape_and_pose(morphable_model, blendshapes, landmark_collection, landmark_mapper, image_width, image_height, edge_topology, contour_landmarks, model_contour, num_iterations, num_shape_coefficients_to_fit, lambda, cpp17::nullopt, pca_coeffs, blendshape_coeffs, fitted_image_points);
  return std::make_tuple(result.first, result.second, pca_coeffs, blendshape_coeffs);
  },
  "Fit the pose (camera), shape model, and expression blendshapes to landmarks, in an iterative way. Returns a tuple (mesh, rendering_parameters, shape_coefficients, blendshape_coefficients).",
  