input: Write a python function to parse an XML document and print out its elements.
  assert parse_xml_document('<note><to>Tove</to><from>Jani</from><heading>Reminder</heading><body>Don't forget me this weekend!</body></note>') == ['to: Tove', 'from: Jani', 'heading: Reminder', 'body: Don\'t forget me this weekend!']
  assert parse_xml_document('<root><child1>Content1</child1><child2>Content2</child2></root>') == ['child1: Content1', 'child2: Content2']
  assert parse_xml_document('<data><item>Value1</item><item>Value2</item></data>') == ['item: Value1', 'item: Value2']
output: def parse_xml_document(xml_string):
      from xml.etree import ElementTree as ET
      root = ET.fromstring(xml_string)
      result = []
      for elem in root:
          result.append(f"{elem.tag}: {elem.text}")
      return result