Minecraft wiki entry for Placed_feature, associated text: surface_relative_threshold_filter—Either returns the current position or nothing. Checks if the surface is inside a range.
 heightmap: The heightmap to use. One of MOTION_BLOCKING, MOTION_BLOCKING_NO_LEAVES, OCEAN_FLOOR, OCEAN_FLOOR_WG, WORLD_SURFACE, or WORLD_SURFACE_WG.
 min_inclusive: The minimum allowed height.
 max_inclusive: The maximum allowed height.