input: def add_large_numbers(num1, num2):
      """
      This function adds two large numbers represented as strings.
      It reverses the input strings, performs digit-by-digit addition with carry,
      and then reverses the result back to get the final sum.
  
      >>> add_large_numbers("111", "1337")
      1448
      >>> add_large_numbers("9999", "1")
      10000
      >>> add_large_numbers("123", "456")
      579
      """
output:     num1 = num1[::-1]
      num2 = num2[::-1]
      carry = 0
      result = []
      max_len = max(len(num1), len(num2))
      
      for i in range(max_len):
          digit1 = int(num1[i]) if i < len(num1) else 0
          digit2 = int(num2[i]) if i < len(num2) else 0
          total = digit1 + digit2 + carry
          carry = total // 10
          result.append(str(total % 10))
      
      if carry:
          result.append(str(carry))
      
      return int(''.join(result[::-1]))