fix unit tests, lower python dependency to 3.9

reasoning_gym/arithmetic/fraction_simplification.py

@@ -82,17 +82,16 @@ class FractionSimplificationDataset(ProceduralDataset):
 
     def _format_fraction(self, num: int, den: int, style: str = "plain") -> str:
         """Format a fraction in various styles"""
-        match style:
-            case "plain":
-                return f"{num}/{den}"
-            case "latex_inline":
-                return f"${num}/{den}$"
-            case "latex_frac":
-                return f"$\\frac{{{num}}}{{{den}}}$"
-            case "latex_dfrac":
-                return f"$\\dfrac{{{num}}}{{{den}}}$"
-            case _:
-                raise ValueError(f"Unknown fraction style: {style}")
+        if style == "plain":
+            return f"{num}/{den}"
+        elif style == "latex_inline":
+            return f"${num}/{den}$"
+        elif style == "latex_frac":
+            return f"$\\frac{{{num}}}{{{den}}}$"
+        elif style == "latex_dfrac":
+            return f"$\\dfrac{{{num}}}{{{den}}}$"
+        else:
+            raise ValueError(f"Unknown fraction style: {style}")
 
     def __getitem__(self, idx: int) -> dict:
         """Generate a single fraction simplification task"""