Added a to_str function for all classes. __str__ function uses it. highscores_data uses the to_str function for saving.

data/score.py

@@ -26,7 +26,7 @@ class Score:
         Returns:
             str: Score class as a string
         """
-        return f"{self.user}: {self.get_str()}"
+        return self.to_str()
 
     @property
     def user(self) -> str:
@@ -67,6 +67,15 @@ class Score:
         """
         return str(self._value)
 
+    def to_str(self) -> str:
+        """
+        Returns Score object as a string.
+
+        Returns:
+            str: string of json representation of Score
+        """
+        return f"{self.user}: {self.get_str()}"
+
 
 class ScoreTime(Score):
     """Class for a time based score. Inherits from Score."""