Add call, get_attr and set_attr methods to VectorEnv (#1600)

* Add call, get_attr and set_attr methods

* Use f-strings and remove assert

* Allow tuples in set_attr and move docstrings

* Replace CubeCrash by CartPole in tests

gym/vector/sync_vector_env.py

@@ -136,6 +136,30 @@ class SyncVectorEnv(VectorEnv):
             infos,
         )
 
+    def call(self, name, *args, **kwargs):
+        results = []
+        for env in self.envs:
+            function = getattr(env, name)
+            if callable(function):
+                results.append(function(*args, **kwargs))
+            else:
+                results.append(function)
+
+        return tuple(results)
+
+    def set_attr(self, name, values):
+        if not isinstance(values, (list, tuple)):
+            values = [values for _ in range(self.num_envs)]
+        if len(values) != self.num_envs:
+            raise ValueError(
+                "Values must be a list or tuple with length equal to the "
+                f"number of environments. Got `{len(values)}` values for "
+                f"{self.num_envs} environments."
+            )
+
+        for env, value in zip(self.envs, values):
+            setattr(env, name, value)
+
     def close_extras(self, **kwargs):
         """Close the environments."""
         [env.close() for env in self.envs]