input: Write a function to add two large numbers represented as strings. The function should return the sum as a string. If any of the input strings is empty, the function should handle it appropriately.
  
  def add_large_numbers(num1, num2):
      if not num1:
          return num2
      if not num2:
          return num1
      
      num1 = num1[::-1]
      num2 = num2[::-1]
      carry = 0
      result = ""
  
      for i in range(max(len(num1), len(num2))):
          if i < len(num1):
              digit1 = int(num1[i])
          else:
              digit1 = 0
          
          if i < len(num2):
              digit2 = int(num2[i])
          else:
              digit2 = 0
          
          sum_total = digit1 + digit2 + carry
          carry = sum_total // 10
          
          result += str(sum_total % 10)
      
      if carry > 0:
          result += str(carry)
      
      return result[::-1]
  
  assert add_large_numbers("111", "1337") == "1448"
  assert add_large_numbers("123", "456") == "579"
  assert add_large_numbers("999", "999") == "1998"
  assert add_large_numbers("", "123") == "123"
  assert add_large_numbers("456", "") == "456"
  assert add_large_numbers("", "") == ""
output: def add_large_numbers(num1, num2):
      if not num1:
          return num2
      if not num2:
          return num1
      
      num1 = num1[::-1]
      num2 = num2[::-1]
      carry = 0
      result = ""
  
      for i in range(max(len(num1), len(num2))):
          if i < len(num1):
              digit1 = int(num1[i])
          else:
              digit1 = 0
          
          if i < len(num2):
              digit2 = int(num2[i])
          else:
              digit2 = 0
          
          sum_total = digit1 + digit2 + carry
          carry = sum_total // 10
          
          result += str(sum_total % 10)
      
      if carry > 0:
          result += str(carry)
      
      return result[::-1]