Verbose flag in play_ scripts depends on inaccessible flag

[itwasabhi]

Trying to run a play script with --verbose as follows: python -m meltingpot.human_players.play_collaborative_cooking --verbose True --print_events True

This results in the following error:

  File "/dev/meltingpot/meltingpot/human_players/play_collaborative_cooking.py", line 65, in verbose_fn
    if env_timestep.observation[f'{lua_index}.{obs}']:
       ~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^
KeyError: '1.ADDED_INGREDIENT_TO_COOKING_POT'

From a quick look through the source code, it seems like susbtrates have a default _ENABLE_DEBUG_OBSERVATIONS = False flag that needs to be manually enabled before the CLI works as intended.

Happy to work on a patch if I can get a suggested fix from a maintainer. Thanks!