Landscape creation using the Python API

Hi,
I am trying to automate the creation of maps using the Python API. At the moment, I already have heightmaps (16-bit grayscale PNG) and am trying to create landscapes with them. I have been trying to spawn unreal.Landscape and unreal.LandsCapeProxy but I get unreal.LandscapePlaceholder everytime.
Could anyone point me in the right direction on how to do this please, the documentation wasn’t really helpful for me ?