input: Write a function to construct an XML document using Python which contains the given list of items. The function should return a string representation of the XML document. If the input list is empty, the function should return an empty string.
  assert get_xml_document(['Item1', 'Item2', 'Item3'])=='<data><item>Item1</item><item>Item2</item><item>Item3</item></data>'
  assert get_xml_document(['Item1'])=='<data><item>Item1</item></data>'
  assert get_xml_document([])==''
output: def get_xml_document(items):
      if not items:
          return ''
      xml_items = ''.join(f'<item>{item}</item>' for item in items)
      return f'<data>{xml_items}</data>'