Fix weight calculation of CooldownModel

The identifier of cooldown weights didn't contained the identifier of
the alternation only the containing rule name and the chosen alternative
index which doesn't informative enough to identify the target point.

grammarinator/runtime/cooldown_model.py

@@ -1,4 +1,4 @@
-# Copyright (c) 2020-2021 Renata Hodovan, Akos Kiss.
+# Copyright (c) 2020-2022 Renata Hodovan, Akos Kiss.
 #
 # Licensed under the BSD 3-Clause License
 # <LICENSE.rst or https://opensource.org/licenses/BSD-3-Clause>.
@@ -14,8 +14,8 @@ def __init__(self, model, weights=None, cooldown=1.0):
         self._cooldown = cooldown
 
     def choice(self, node, idx, choices):
-        i = self._model.choice(node, idx, [w * self._weights.get((node.name, i), 1) for i, w in enumerate(choices)])
-        self._weights[(node.name, i)] = self._weights.get((node.name, i), 1) * self._cooldown
+        i = self._model.choice(node, idx, [w * self._weights.get((node.name, idx, i), 1) for i, w in enumerate(choices)])
+        self._weights[(node.name, idx, i)] = self._weights.get((node.name, idx, i), 1) * self._cooldown
         return i
 
     def quantify(self, node, idx, min, max):