input: from typing import List
  
  def parse_xml(text: str) -> List['Tag']:
      """Parse an XML document and return a list of tag objects.
      >>> parse_xml("""<xml><root><child1 id="1"><subchild1 value="a"></subchild1><subchild2 value="b"></subchild2></child1><child2 id="2"><subchild3 value="c"></subchild3><subchild4 value="d"></subchild4></child2></root></xml>""")
      [Tag(tag_id='1', values=['a', 'b']), Tag(tag_id='2', values=['c', 'd'])]
      """
      
      import xml.etree.ElementTree as ET
  
      class Tag:
          def __init__(self, tag_id):
              self.tag_id = tag_id
              self.values = []
          
          def add_value(self, value):
              self.values.append(value)
      
      tag_objects = []
  
      root = ET.fromstring(text)
      for child in root:
          tag = Tag(child.attrib["id"])
          for subchild in child:
              tag.add_value(subchild.attrib["value"])
          tag_objects.append(tag)
  
      return tag_objects
output:     import xml.etree.ElementTree as ET
  
      class Tag:
          def __init__(self, tag_id):
              self.tag_id = tag_id
              self.values = []
          
          def add_value(self, value):
              self.values.append(value)
          
          def __repr__(self):
              return f"Tag(tag_id='{self.tag_id}', values={self.values})"
      
      tag_objects = []
  
      root = ET.fromstring(text)
      for child in root:
          tag = Tag(child.attrib["id"])
          for subchild in child:
              tag.add_value(subchild.attrib["value"])
          tag_objects.append(tag)
  
      return tag_objects