feat:openenv rollout_func (#3239) [skip ci]

* feat:openenv rollout_func

* chore lint

* docs

* add:docs processing_class

* tests

* lint

tests/utils/test_grpo_rw_fnc.py

@@ -0,0 +1,18 @@
+import os
+
+import pytest
+
+from axolotl.core.trainers.grpo import GRPOStrategy
+
+
+def test_get_rollout_func_loads_successfully():
+    """Test that a valid rollout function can be loaded"""
+    rollout_func = GRPOStrategy.get_rollout_func("os.path.join")
+    assert callable(rollout_func)
+    assert rollout_func == os.path.join
+
+
+def test_get_rollout_func_invalid_module_raises_error():
+    """Test that invalid module path raises clear ValueError"""
+    with pytest.raises(ValueError, match="Rollout function .* not found"):
+        GRPOStrategy.get_rollout_func("nonexistent_module.my_func")