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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_command(arguments):
 """Utility function to extract command from docopt arguments. :param arguments: :return: command """

    cmds = list(filter(lambda k: not (k.startswith('-') or
                                 k.startswith('<')) and arguments[k],
                  arguments.keys()))
    if len(cmds) != 1:
        raise Exception('invalid command line!')
    return cmds[0]