input: Write a function to check if a given number is an Armstrong number. If the number is an Armstrong number return True, else return False. If the given number is 0, return True.
  assert is_armstrong_number(153)==True
  assert is_armstrong_number(370)==True
  assert is_armstrong_number(1253)==False
  assert is_armstrong_number(0)==True
  assert is_armstrong_number(1)==True
output: def is_armstrong_number(num):
      num_str = str(num)
      num_digits = len(num_str)
      sum_of_powers = sum(int(digit) ** num_digits for digit in num_str)
      return sum_of_powers == num