Fixing np_random att visibility in core.Task class

[qgallouedec]

Hi, can you elaborate about the need behind that PR?

[drmateo]

Sure! This patch is more a style problem that must be resolved as I purpose. The two main reasons are:

• Attribute np_random is a member attribute of the Task class, so for the sake of readability this attribute must be first declared in Task.init method, instead of in another secondary class as it was the case before this patch; it was first declared in reset method of RobotTaskEnv. That made a little difficult to track the origin of att Task.np_random
• The other problem is, that this patch resolves problems with syntax check tools such as Pylance. Mainly, inability to resolve attributo Task.np_random.

[qgallouedec]

Sounds fair. However, I would rather go for a set_np_random(np_random) instead of the set_random_seed(seed). By the way, this method shouldn't be protected, as it its intended to be called outside the class.