Returns default metric specs for multi-class classification problems.

model_names Optional model names if multi-model evaluation.
output_names Optional list of output names (if multi-output model).
output_weights Optional output weights for creating overall metric aggregated across outputs (if multi-output model). If a weight is not provided for an output, it's weight defaults to 0.0 (i.e. output ignored).
binarize Optional settings for binarizing multi-class/multi-label metrics.
aggregate Optional settings for aggregating multi-class/multi-label metrics.
sparse True if the labels are sparse.