input: Write a function to add two large numbers represented as strings and return the result as a string.
  assert add_large_numbers("111", "1337") == "1448"
  assert add_large_numbers("0", "0") == "0"
  assert add_large_numbers("999", "1") == "1000"
  assert add_large_numbers("123", "456") == "579"
  assert add_large_numbers("54321", "12345") == "66666"
output: def add_large_numbers(num1, num2):
      return str(int(num1) + int(num2))