@classmethod
def generate_toy_data(cls, reco_vector, size=None):
    """Generate toy data according to the expectation values.

        The reco vector can have a shape ``([c,d,]n_reco_bins,)``. Assuming the
        data is of shape ``([a,b,...,]n_reco_bins,)``, the output will be of
        shape ``([a,b,...,][c,d,...,])``.

        """
    raise NotImplementedError('Must be implemented in a subclass!')
