Fix bug in the MultifolderWithCache.seed method and add a test

Signed-off-by: EBoguslawski <eva.boguslawski@gmail.com>

grid2op/Chronics/multifolderWithCache.py

@@ -291,7 +291,7 @@ def seed(self, seed : int):
         """
         res = super().seed(seed)
         max_int = np.iinfo(dt_int).max
-        self._cached_seeds = np.empty(shape=self._order.shape, dtype=dt_int)
+        self._cached_seeds = np.empty(len(shape=self._cached_data), dtype=dt_int)
         for i in self._order:
             data = self._cached_data[i]
             seed_ts = self.space_prng.randint(max_int)

grid2op/tests/test_MultifolderWithCache_seed.py

@@ -0,0 +1,42 @@
+# Copyright (c) 2023, RTE (https://www.rte-france.com)
+# See AUTHORS.txt
+# This Source Code Form is subject to the terms of the Mozilla Public License, version 2.0.
+# If a copy of the Mozilla Public License, version 2.0 was not distributed with this file,
+# you can obtain one at http://mozilla.org/MPL/2.0/.
+# SPDX-License-Identifier: MPL-2.0
+# This file is part of Grid2Op, Grid2Op a testbed platform to model sequential decision making in power systems.
+
+# %%
+import os
+import grid2op
+from grid2op.Chronics import MultifolderWithCache
+import unittest
+import warnings
+
+module_name = MultifolderWithCache.__module__
+module = __import__(module_name)
+file_path = module.__file__
+print(f"Library path: \n{file_path}")
+
+class TestMultifolderWithCacheSeed(unittest.TestCase):
+    def test_box_action_space(self):
+
+        with warnings.catch_warnings():
+            warnings.filterwarnings("ignore")
+            env = grid2op.make("l2rpn_case14_sandbox", test=True, _add_to_name=type(self).__name__,
+                               chronics_class=MultifolderWithCache)
+
+        # I take the last chronics on purpose so that its index is larger than the number of selected chronics (only one here)
+        env.chronics_handler.real_data.set_filter(lambda x: os.path.basename(x) == "0002")
+        env.chronics_handler.reset()
+
+        try:
+            env.reset(seed=0)
+        except Exception as e:
+            self.fail(f"{type(self).__name__} raised an exception: {e}")
+
+
+
+# %%        
+if __name__ == "__main__":
+    unittest.main()