input: from typing import List
  
  def parse_xml(text: str) -> List[Tag]:
      """ Parses an XML document and returns a list of Tag objects.
      Each Tag object represents a child element with its id and a list of values from its subchild elements.
      >>> 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 id=1 values=['a', 'b']>, <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):
          self.tag_id = tag_id
          self.values = []
      
      def add_value(self, value):
          self.values.append(value)
  
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 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
  