input: Write a python function to sort a list of numbers using radix sort.
  assert radix_sort([15, 79, 25, 68, 37]) == [15, 25, 37, 68, 79]
  assert radix_sort([9, 11, 8, 7, 3, 2]) == [2, 3, 7, 8, 9, 11]
  assert radix_sort([36, 12, 24, 26, 29]) == [12, 24, 26, 29, 36]
output: def radix_sort(nums):
      if len(nums) == 0:
          return nums
  
      def counting_sort(nums, exp):
          n = len(nums)
          output = [0] * n
          count = [0] * 10
          
          for i in range(0, n):
              index = nums[i] // exp
              count[index % 10] += 1
              
          for i in range(1, 10):
              count[i] += count[i - 1]
              
          i = n - 1
          while i >= 0:
              index = nums[i] // exp
              output[count[index % 10] - 1] = nums[i]
              count[index % 10] -= 1
              i -= 1
              
          for i in range(0, len(nums)):
              nums[i] = output[i]
  
      max_num = max(nums)
      exp = 1
      while max_num // exp > 0:
          counting_sort(nums, exp)
          exp *= 10
          
      return nums