def p(self, value, event):
assert isinstance(value, bool)<EOL>ptrue = self.cpt[event_values(event, self.parents)]<EOL>return if_(value, ptrue, <NUM_LIT:1> - ptrue)<EOL>
Return the conditional probability
        P(X=value | parents=parent_values), where parent_values
        are the values of parents in event. (event must assign each
        parent a value.)
        >>> bn = BayesNode('X', 'Burglary', {T: 0.2, F: 0.625})
        >>> bn.p(False, {'Burglary': False, 'Earthquake': True})
        0.375