add param docs for DriverVectorCube __init__ Open-EO/openeo-geopyspar…

…k-driver#663

openeo_driver/datacube.py

@@ -258,10 +258,10 @@ def __init__(
         cube: Optional[xarray.DataArray] = None,
     ):
         """
-
-        :param geometries:
-        :param cube:
-        :param flatten_prefix: prefix for column/field/property names when flattening the cube
+        :param geometries: GeoDataFrame with geometries and properties.
+        :param cube: Optional DataArray with dimensions (geometry (r), time (o), bands/properties (o)),
+            r = required, o = optional.
+        Note that cube can only have a single dtype. For e.g. vector_to_raster, we'd like to keep this numeric.
         """
         # TODO #114 EP-3981: lazy loading (like DelayedVector)?
         if cube is not None: