Max timesteps calculation
# the maximum number of episode steps is determined by :
#
# timedelay_factor * alpha * (grid_width + grid_height + (number_of_agents/number_of_cities)) # noqa
#
# in the current sprase rail generator, the ratio of
# `number_of_agents/number_of_cities` is roughly 20
#
# TODO: the serialized env should include the max allowed timesteps per
# env, and should ideally be returned by the rail generator
self.env._max_episode_steps = \
int(4 * 2 * (self.env.width + self.env.height + 20))
