Unsure of best way to access xr.Dataset methods

[TomNicholas]

(described in more detail at pydata/xarray#2473)

I want to make a BoutDataset class which contains extra attributes to hold information about the run which doesn't naturally fit into the xarray data model, extra methods to perform analysis/plotting which only users of this code would require, but also be able to use xarray-specific methods and top-level functions:

bd = BoutDataset('/path/to/data')

ds = bd.data  # access the wrapped xarray dataset
extra_data = bd.extra_data  # access the BOUT-specific data

bd.isel(time=-1)  # use xarray dataset methods

bd2 = BoutDataset('/path/to/other/data')
concatenated_bd = xr.concat([bd, bd2])  # apply top-level xarray functions to the data

bd.plot_tokamak()  # methods implementing bout-specific functionality

I'm not sure what the best way to do this is. My current approach uses xr.register_dataset_accessor.

[TomNicholas]

This was closed by adding the ability to always keep attributes on operations in xarray (pydata/xarray#2482).

This means that as long as the desired data is stored either in the dataset variables or in the attrs dictionary it will be preserved across operations, and therefore we can just use xarray.Dataset to hold everything, and implement BOUT-specific methods using the xarray accessors.