code: def test_letter_name(self):
      self.assertEqual(letter_name(0), "a")
      self.assertEqual(letter_name(4), "e")
      self.assertEqual(letter_name(25), "z")
      self.assertEqual(letter_name(30), "ee")
      self.assertEqual(letter_name(77), "zzz")
  
file_path: agate/tests/test_utils.py
imports: import unittest
  from decimal import Decimal
  from agate.utils import Quantiles, letter_name, round_limits
label_desc: Use image node_id 2 for calling the TestMisc obj's underlying member method code with example usage: obj.test_letter_name() without return types