How can I develop my own local planner with isaac sdk?

Hi,
I want to develop a custom local planner with collision avoidance, but I do not know how to get obstacles by isaac sdk.
Where can I find the helper function for ObstacleWorld or How can I do this?

Thanks

Could you please review these examples and let us know if it helps. Thanks
http://isaac.nvidia.com/isaac-2019.2-dev/isaac/doc/message_api.html?highlight=get%20obstacle#distancemapproto