LearningProblemGenerator not working

[alkidbaci]

Class LearningProblemGenerator from learning_problem_generator.py is currently not working.
When you try to use it the following error arises:

AttributeError: 'RL_State' object has no attribute 'instances'

Solution:

1. Either fix the issue
2. Deprecate LearningProblemGenerator and use LPGen instead.