code: def write_generator_cost_data(self, file):
          
          file.write("\n%%%% generator cost data\n")
          file.write("%%\t1\tstartup\tshutdown\tn\tx1\ty1\t...\txn\tyn\n")
          file.write("%%\t2\tstartup\tshutdown\tn\tc(n-1)\t...\tc0\n")
          file.write("%sgencost = [\n" % self._prefix)
  
          for generator in self.case.generators:
              n = len(generator.p_cost)
              template = '\t%d\t%g\t%g\t%d'
              for _ in range(n):
                  template = '%s\t%%g' % template
              template = '%s;\n' % template
  
              if generator.pcost_model == PW_LINEAR:
                  t = 2
  #                cp = [p for p, q in generator.p_cost]
  #                cq = [q for p, q in generator.p_cost]
  #                c = zip(cp, cq)
                  c = [v for pc in generator.p_cost for v in pc]
              elif generator.pcost_model == POLYNOMIAL:
                  t = 1
                  c = list(generator.p_cost)
              else:
                  raise
  
              vals = [t, generator.c_startup, generator.c_shutdown, n] + c
  
              file.write(template % tuple(vals))
          file.write("];\n")
docs: Writes generator cost data to file.