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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_default_shell():
 """ return the path to the default shell for the current user. """

    if is_windows():
        return 'cmd.exe'
    else:
        import pwd
        import getpass

        if 'SHELL' in os.environ:
            return os.environ['SHELL']
        else:
            username = getpass.getuser()
            shell = pwd.getpwnam(username).pw_shell
            return shell