Documentation - Missing doc string

https://gitlab.aicrowd.com/flatland/flatland/blob/master/flatland/envs/observations.py#L500 https://gitlab.aicrowd.com/flatland/flatland/blob/master/flatland/envs/observations.py#L508 https://gitlab.aicrowd.com/flatland/flatland/blob/master/flatland/envs/observations.py#L521 https://gitlab.aicrowd.com/flatland/flatland/blob/master/flatland/envs/observations.py#L526 https://gitlab.aicrowd.com/flatland/flatland/blob/master/flatland/envs/observations.py#L555 https://gitlab.aicrowd.com/flatland/flatland/blob/master/flatland/envs/observations.py#L563 https://gitlab.aicrowd.com/flatland/flatland/blob/master/flatland/envs/observations.py#L642 https://gitlab.aicrowd.com/flatland/flatland/blob/master/flatland/envs/observations.py#L654 https://gitlab.aicrowd.com/flatland/flatland/blob/master/flatland/envs/observations.py#L703

Missing doc string in these function.