[Update core.py]: comment the support for with-statement
diff --git a/gym/core.py b/gym/core.py
index 11ba5842d1e..8657afdec2d 100644
--- a/gym/core.py
+++ b/gym/core.py
@@ -145,9 +145,11 @@ def __str__(self):
             return '<{}<{}>>'.format(type(self).__name__, self.spec.id)
 
     def __enter__(self):
+        """Support with-statement for the environment. """
         return self
 
     def __exit__(self, *args):
+        """Support with-statement for the environment. """
         self.close()
         # propagate exception
         return False
