def test1(self):
   self.assertEqual(base_str(10,10), "10")
 def test2(self):
   self.assertEqual(base_str(10,60), "a")
 def test7(self):
   self.assertEqual(base_str(4,51), "4")
 def test6(self):
   self.assertEqual(base_str(-1351), "-lN")
 def test5(self):
   self.assertEqual(base_str(-1351,62), "-lN")
 def test4(self):
   with self.assertRaises(ValueError):
     base_str(60,63)
 def test3(self):
   self.assertEqual(base_str(1351,62), "lN")