input: Write a function to add two large numbers represented as strings. The function should return the sum of the two numbers as a string. If one of the strings is empty, it should be treated as "0".
  assert add_large_numbers("111", "1337") == "1448"
  assert add_large_numbers("999", "1") == "1000"
  assert add_large_numbers("", "567") == "567"
  assert add_large_numbers("888", "") == "888"
  assert add_large_numbers("", "") == "0"
output: def add_large_numbers(num1, num2):
      if not num1:
          num1 = "0"
      if not num2:
          num2 = "0"
      return str(int(num1) + int(num2))