input: Write a function to check if a number is divisible by a given divisor.
  assert is_divisible(10, 2) == True
  assert is_divisible(10, 3) == False
  assert is_divisible(25, 5) == True
  assert is_divisible(25, 4) == False
output: def is_divisible(number, divisor):
      return number % divisor == 0