Write generator data as CSV.

def write_generator_data(self, file):
        """ Write generator data as CSV.
        """
        writer = self._get_writer(file)
        writer.writerow(["bus"] + GENERATOR_ATTRS)

        for g in self.case.generators:
            i = g.bus._i
            writer.writerow([i] + [getattr(g,a) for a in GENERATOR_ATTRS])