code: def __prepare(self, filestem, pos, neg, b):
          
          posFile = open('%s/%s.f' % (self.tmpdir, filestem), 'w')
          negFile = open('%s/%s.n' % (self.tmpdir, filestem), 'w')
          bFile = open('%s/%s.b' % (self.tmpdir, filestem), 'w')
  
          posFile.write(pos)
          negFile.write(neg)
          bFile.write(b)
  
          posFile.close()
          negFile.close()
          bFile.close()
docs: Prepares the needed files.