old_contents: import random
  
  from base import PyexcelSheetBase
  
  
  class SheetAccessTest(PyexcelSheetBase):
      @staticmethod
      def get_random_char():
          i = random.randint(97, 122)
          return chr(i)
  
      def test_out_of_bounds_write(self):
          value = self.get_random_char()
          column = self.get_random_char() + self.get_random_char()
          cell = column + str(random.randint(1, 30))
          self.sheet[cell] = value
  
          self.assertEqual(value, self.sheet[cell])
  
      def test_out_of_bounds_read(self):
          with self.assertRaises(IndexError):
              self[0, 20]
  
          with self.assertRaises(IndexError):
              self[20, 0]
  
new_contents: import random
  
  from base import PyexcelSheetBase
  
  
  class TestSheetAccess(PyexcelSheetBase):
      @staticmethod
      def get_random_char():
          i = random.randint(97, 122)
          return chr(i)
  
      def test_out_of_bounds_write(self):
          value = self.get_random_char()
          column = self.get_random_char() + self.get_random_char()
          cell = column + str(random.randint(1, 30))
          self.sheet[cell] = value
  
          self.assertEqual(value, self.sheet[cell])
  
      def test_out_of_bounds_read(self):
          with self.assertRaises(IndexError):
              self[0, 20]
  
          with self.assertRaises(IndexError):
              self[20, 0]
  
subject: rename test class