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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 get_config_directory(appname):
 """ Get OS-specific configuration directory. :type appname: str :arg appname: capitalized name of the application """

    if platform.system().lower() == 'windows':
        path = os.path.join(os.getenv('APPDATA') or '~', appname, appname)
    elif platform.system().lower() == 'darwin':
        path = os.path.join('~', 'Library', 'Application Support', appname)
    else:
        path = os.path.join(os.getenv('XDG_CONFIG_HOME') or '~/.config',
                            appname.lower())
    return os.path.expanduser(path)