Implement songs in unique dirs

karaokatalog/Library.py

@@ -42,4 +42,12 @@ class Library:
         For deduplication, it is helpful to assume every song is in its own directory. This returns a sequence of songs filtered so
         that there are no two songs sharing the same base dir. This filtering is done arbitrarily.
         """
-        raise NotImplementedError()  # TODO Implement
+        unique_dirs: set[Path] = set()
+        songs_in_unique_dirs: list[Song] = []
+
+        for song in self.songs:
+            if song.dir not in unique_dirs:
+                songs_in_unique_dirs.append(song)
+                unique_dirs.add(song.dir)
+
+        return tuple(songs_in_unique_dirs)