def builddataset(self, dataset):
raise NotImplementedError("<STR_LIT>")<EOL>
Extract fit dataset from :class:`gvar.dataset.Dataset` ``dataset``.

        The code  ::

            import gvar as gv

            data = gv.dataset.avg_data(m.builddataset(dataset))

        that builds data for model ``m`` should be functionally
        equivalent to ::

            import gvar as gv

            data = m.builddata(gv.dataset.avg_data(dataset))

        This method is optional. It is used only by
        :meth:`MultiFitter.process_dataset`.

        Args:
            dataset: :class:`gvar.dataset.Dataset` (or similar dictionary)
                dataset containing the fit data for all models. This is
                typically a dictionary, whose keys are the ``datatag``\s of
                the models.