741 added a GaussianProcessRegression abstract method _ensure_variable_model_data. This is an unnecessary breaking change, as some subclasses may not need to implement this (and any that do should know about it by failing garden path tests). This PR makes it optional instead.
741 added a
GaussianProcessRegressionabstract method_ensure_variable_model_data. This is an unnecessary breaking change, as some subclasses may not need to implement this (and any that do should know about it by failing garden path tests). This PR makes it optional instead.