input: Write a function to extract phone numbers that start with '08' from a given list. The function should return a new list containing only the phone numbers that start with '08'. If the input list is empty, the function should return an empty list.
  assert extract_08_numbers(['0834567', '0945678', '07123456', '08901234', '07890123'])==['0834567', '08901234']
  assert extract_08_numbers(['0912345', '07654321', '08012345'])==['08012345']
  assert extract_08_numbers(['07123456', '09876543'])==[]
  assert extract_08_numbers([])==[]
output: def extract_08_numbers(phone_numbers):
      return [num for num in phone_numbers if num.startswith('08')]