With the new Automatic Colour Conversion Graph implemented, we should discourage usage of the colour.models.XYZ_to_colourspace_model definition. It has been a convenient wrapper but it should disappear because its functionality is superseded by the colour.convert definition.

Deprecating API features is done by using the various objects in the colour.utilities.deprecation module. In this case, the API_CHANGES dictionary should be updated with a new key along those lines:

API_CHANGES = {
    'FutureRemove': [
        '`colour.models.XYZ_to_colourspace_model',
    ],
    [...]
}