feat: add method to check if a shot has obersvations

Author: fabianschenk

opensfm/src/sfm/src/tracks_manager.cc

@@ -123,6 +123,8 @@ int TracksManager::NumShots() const { return tracks_per_shot_.size(); }
 
 int TracksManager::NumTracks() const { return shots_per_track_.size(); }
 
+bool TracksManager::HasShotObservations(const ShotId& shot) const { return tracks_per_shot_.count(shot) > 0; }
+
 std::vector<ShotId> TracksManager::GetShotIds() const {
   std::vector<ShotId> shots;
   shots.reserve(tracks_per_shot_.size());

opensfm/src/sfm/tracks_manager.h

@@ -45,6 +45,8 @@ class TracksManager {
   static TracksManager InstanciateFromString(const std::string& str);
   std::string AsSring()const;
 
+  bool HasShotObservations(const ShotId& shot) const;
+
   static std::string TRACKS_HEADER;
   static int TRACKS_VERSION;