class_docstr: Simple python implementation of transitions collection non-episodic memories
  are constructed on top of.
code: def __getitem__(self, key: int):
      # NOTE: we can switch to a method which fetches multiple items at a time
      # if that would significantly improve performance
      pass
  
file_path: coach/rl_coach/memories/non_episodic/transition_collection.py
imports: from rl_coach.core_types import Transition
label_desc: Use image node_id 6 for calling the TransitionCollection obj's underlying member method code with example usage: obj.__getitem__(key) without return types