input: Write a function that checks if a given number is an Armstrong number. An Armstrong number is a number that is equal to the sum of its own digits each raised to the power of the number of digits.
  
  
  def is_armstrong_number(num):
  # your code here
      return
  
  assert is_armstrong_number(153)==True
  assert is_armstrong_number(9474)==True
  assert is_armstrong_number(123)==False
  assert is_armstrong_number(371)==True
  assert is_armstrong_number(407)==True
  
output: def is_armstrong_number(num):
      digits = str(num)
      power = len(digits)
      sum_of_powers = sum(int(digit) ** power for digit in digits)
      return sum_of_powers == num