input: Write a python function to print items from a list that start with the letter 'a'.
  assert print_items_starting_with_a(["apple", "banana", "orange", "avocado"])==["apple", "avocado"]
  assert print_items_starting_with_a(["apricot", "blueberry", "grape", "kiwi"])==["apricot"]
  assert print_items_starting_with_a(["pear", "plum", "peach", "pineapple"])==[]
output: def print_items_starting_with_a(items):
      return [item for item in items if item.startswith('a')]