input: Write a Python function to paginate a list of items with 3 items per page.
  assert page_items(["apple", "banana", "carrot", "date", "elderberry", "fig", "grape", "honeydew", "iceberg lettuce"], 1) == ["apple", "banana", "carrot"]
  assert page_items(["apple", "banana", "carrot", "date", "elderberry", "fig", "grape", "honeydew", "iceberg lettuce"], 2) == ["date", "elderberry", "fig"]
  assert page_items(["apple", "banana", "carrot", "date", "elderberry", "fig", "grape", "honeydew", "iceberg lettuce"], 3) == ["grape", "honeydew", "iceberg lettuce"]
  assert page_items(["apple", "banana", "carrot", "date", "elderberry", "fig", "grape", "honeydew", "iceberg lettuce"], 4) == []
output: def page_items(items, page):
      items_per_page = 3
      start_index = (page - 1) * items_per_page
      end_index = start_index + items_per_page
      return items[start_index:end_index]