'Generate a default rule, which mimics a majority classifier.
Specific to each individual rule inducer, the application of the
default rule varies. To predict an instance, a single default
rule should be considered.
Parameters
X, Y, W : ndarray
Learning data.
domain : Orange.data.domain.Domain
Data domain, used to calculate class distributions.
Returns
default_rule : Rule
Default rule with no selectors that covers all learning
instances and mimics a majority classifier.'

def generate_default_rule(self, X, Y, W, domain):

    rf = self.rule_finder
    dist = get_dist(Y, W, domain)
    default_rule = Rule(None, None, self.domain, dist, dist, rf.quality_evaluator, rf.complexity_evaluator, rf.significance_validator, rf.general_validator)
    default_rule.filter_and_store(X, Y, W, None)
    default_rule.do_evaluate()
    default_rule.create_model()
    return default_rule
