support python 3.10 (#450)

* support python 3.10

* add 3.10 to tests

* new StrEnum

reasoning_gym/utils.py

@@ -1,6 +1,7 @@
 import math
 import re
 from decimal import Decimal, InvalidOperation
+from enum import Enum
 from fractions import Fraction
 from typing import Any, Optional, Union
 
@@ -117,3 +118,38 @@ def compute_decimal_reward(answer: Optional[str], oracle_answer: str, strip_comm
             reward = len(oracle_answer) / len(answer)
 
     return reward
+
+
+class StrEnum(str, Enum):
+    """
+    Taken from Python 3.11 StrEnum implementation, moved here to support Python 3.10.
+    Enum where members are also (and must be) strings
+    """
+
+    def __new__(cls, *values):
+        "values must already be of type `str`"
+        if len(values) > 3:
+            raise TypeError("too many arguments for str(): %r" % (values,))
+        if len(values) == 1:
+            # it must be a string
+            if not isinstance(values[0], str):
+                raise TypeError("%r is not a string" % (values[0],))
+        if len(values) >= 2:
+            # check that encoding argument is a string
+            if not isinstance(values[1], str):
+                raise TypeError("encoding must be a string, not %r" % (values[1],))
+        if len(values) == 3:
+            # check that errors argument is a string
+            if not isinstance(values[2], str):
+                raise TypeError("errors must be a string, not %r" % (values[2]))
+        value = str(*values)
+        member = str.__new__(cls, value)
+        member._value_ = value
+        return member
+
+    @staticmethod
+    def _generate_next_value_(name, start, count, last_values):
+        """
+        Return the lower-cased version of the member name.
+        """
+        return name.lower()