add a new method for finding the timestamp when the expert was last v…

…alid

nocturne/cpp/include/scenario.h

@@ -115,6 +115,17 @@ class Scenario : public sf::Drawable {
   // void removeVehicle(Vehicle* object);
   bool RemoveObject(const Object& object);
 
+  // Return the last timestamp where the object is valid
+  int64_t ExpertLastValid(const Object& object) const {
+    // expert_valid_masks is an array of 0s and 1s
+    // we want to return the last index where the object is valid
+    // so we reverse the array and find the first index where the object is valid
+    // and then subtract that from the size of the array
+    const auto& valid_mask = expert_valid_masks_.at(object.id());
+    auto it = std::find(valid_mask.rbegin(), valid_mask.rend(), true);
+    return valid_mask.size() - std::distance(valid_mask.rbegin(), it);
+  }
+
   // Returns expert position for obj at timestamp.
   geometry::Vector2D ExpertPosition(const Object& obj,
                                     int64_t timestamp) const {

nocturne/pybind11/src/scenario.cc

@@ -72,6 +72,7 @@ void DefineScenario(py::module& m) {
       .def("expert_pos_shift", &Scenario::ExpertPosShift)
       .def("expert_heading_shift", &Scenario::ExpertHeadingShift)
       .def("expert_position", &Scenario::ExpertPosition)
+      .def("expert_last_valid", &Scenario::ExpertLastValid)
 
       // TODO: Deprecate the legacy interfaces below.
       .def("getVehicles", &Scenario::vehicles,