input: Write a python function to classify a list of numbers as valid or invalid, where a valid list contains only numbers between 0 and 1.
  assert classify([0, 0.5, 1]) == True
  assert classify([0, -0.5, 1]) == False
  assert classify([0, 1.5, 1]) == False
  assert classify([0.2, 0.8, 0.9]) == True
output: def classify(numbers):
      return all(0 <= num <= 1 for num in numbers)