input: from typing import List
  import xml.etree.ElementTree as ET
  
  def parse_xml(text: str) -> List[Tag]:
      """ Parses an XML document and returns a list of tag objects. Each tag object
      contains an id and a list of values from its subchildren.
      >>> 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'])]
      """
      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
  
  class Tag:
      def __init__(self, tag_id: str):
          self.tag_id = tag_id
          self.values = []
      
      def add_value(self, value: str):
          self.values.append(value)
output:     def __repr__(self):
          return f"Tag(tag_id='{self.tag_id}', values={self.values})"