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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def do_tortoisehg_report(repos, output):
 """ Generate a thg-reporegistry.xml file from a list of repos and print to output Args: repos (iterable):
 iterable of Repository subclass instances output (writeable):
 output stream to which THG XML will be printed """

    import operator
    import xml.etree.ElementTree as ET

    root = ET.Element('reporegistry')
    item = ET.SubElement(root, 'treeitem')

    group = ET.SubElement(item, 'group', attrib=Dict(name='groupname'))

    def fullname_to_shortname(fullname):
        """
        Return a TortoiseHG-friendly path to a repository

        Args:
            fullname (str): path to repository

        Returns:
            str: path with $HOME replaced with ``~`` and leading ``./``
                stripped
        """
        shortname = fullname.replace(os.environ['HOME'], '~')
        shortname = shortname.lstrip('./')
        return shortname

    for repo in sorted(repos, key=operator.attrgetter('fpath')):
        fullname = os.path.join(
            os.path.dirname(repo.fpath),
            os.path.basename(repo.fpath))
        shortname = fullname_to_shortname(fullname)
        if repo.prefix != '.hg':
            shortname = "%s%s" % (shortname, repo.prefix)
        _ = ET.SubElement(group, 'repo',
                          attrib=Dict(
                              root=repo.fpath,
                              shortname=shortname,
                              basenode='0'*40))
        _
    print('<?xml version="1.0" encoding="UTF-8"?>', file=output)
    print("<!-- autogenerated: %s -->" % "TODO", file=output)
    print(ET.dump(root), file=output)