Topological ML data

[peterdudfield]

Describe the bug
Topological data is not coverted from xr.Dataset properly

To Reproduce
run this tests/test_netcdf_dataset.py and see that batchML has not topological data in it

** additional context **
These files are being moved from nowcasting_dataset, so its good not didnt want to make this change there.

Currently:

•    if TOPOGRAPHIC_DATA in xr_dataset.keys():
  

•        return TopographicML(
  

•            batch_size=xr_dataset[TOPOGRAPHIC_DATA].shape[0],
  

•            topo_data=xr_dataset[TOPOGRAPHIC_DATA],
  

•            topo_x_coords=xr_dataset[TOPOGRAPHIC_DATA].topo_x,
  

•            topo_y_coords=xr_dataset[TOPOGRAPHIC_DATA].topo_y,
  

•        )
  

•    else:
  

•        return None
  

Potential solution
+

•    return TopographicML(
  

•        batch_size=xr_dataset.data.shape[0],
  

•        topo_data=xr_dataset.data,
  

•        topo_x_coords=xr_dataset.x,
  

•        topo_y_coords=xr_dataset.y,
  

•    )