unified API wrapper and updated examples

alr_envs/dmc/ball_in_cup/ball_in_the_cup_mp_wrapper.py

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+from typing import Tuple, Union
+
+import numpy as np
+
+from mp_env_api.interface_wrappers.mp_env_wrapper import MPEnvWrapper
+
+
+class DMCBallInCupMPWrapper(MPEnvWrapper):
+
+    @property
+    def active_obs(self):
+        # Besides the ball position, the environment is always set to 0.
+        return np.hstack([
+            [False] * 2,  # cup position
+            [True] * 2,  # ball position
+            [False] * 2,  # cup velocity
+            [False] * 2,  # ball velocity
+        ])
+
+    @property
+    def current_pos(self) -> Union[float, int, np.ndarray]:
+        return np.hstack([self.physics.named.data.qpos['cup_x'], self.physics.named.data.qpos['cup_z']])
+
+    @property
+    def current_vel(self) -> Union[float, int, np.ndarray, Tuple]:
+        return np.hstack([self.physics.named.data.qvel['cup_x'], self.physics.named.data.qvel['cup_z']])
+
+    @property
+    def goal_pos(self) -> Union[float, int, np.ndarray, Tuple]:
+        raise ValueError("Goal position is not available and has to be learnt based on the environment.")
+
+    @property
+    def dt(self) -> Union[float, int]:
+        return self.env.dt