code: def sum_out(self, var, bn):
          "Make a factor eliminating var by summing over its values."
          vars = [X for X in self.vars if X != var]
          cpt = dict((event_values(e, vars),
                      sum(self.p(extend(e, var, val))
                          for val in bn.variable_values(var)))
                     for e in all_events(vars, bn, {}))
          return Factor(vars, cptf sum_out(self, var, bn):
          "Make a factor eliminating var by summing over its values."
          vars = [X for X in self.vars if X != var]
          cpt = dict((event_values(e, vars),
                      sum(self.p(extend(e, var, val))
                          for val in bn.variable_values(var)))
                     for e in all_events(vars, bn, {}))
          return Factor(vars, cpt)
docs: Make a factor eliminating var by summing over its values.