fixed OpenAI fetch tasks; added nicer imports

alr_envs/open_ai/classic_control/continuous_mountain_car/__init__.py

@@ -0,0 +1 @@
+from .mp_wrapper import MPWrapper

alr_envs/open_ai/classic_control/continuous_mountain_car/mp_wrapper.py

@@ -0,0 +1,22 @@
+from typing import Union
+
+import numpy as np
+from mp_env_api import MPEnvWrapper
+
+
+class MPWrapper(MPEnvWrapper):
+    @property
+    def current_vel(self) -> Union[float, int, np.ndarray]:
+        return np.array([self.state[1]])
+
+    @property
+    def current_pos(self) -> Union[float, int, np.ndarray]:
+        return np.array([self.state[0]])
+
+    @property
+    def goal_pos(self):
+        raise ValueError("Goal position is not available and has to be learnt based on the environment.")
+
+    @property
+    def dt(self) -> Union[float, int]:
+        return 0.02