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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 create_strategy(name=None):
 """ Create a strategy, or just returns it if it's already one. :param name: :return: Strategy """

    import logging
    from bonobo.execution.strategies.base import Strategy

    if isinstance(name, Strategy):
        return name

    if name is None:
        name = DEFAULT_STRATEGY

    logging.debug("Creating execution strategy {!r}...".format(name))

    try:
        factory = STRATEGIES[name]
    except KeyError as exc:
        raise RuntimeError(
            "Invalid strategy {}. Available choices: {}.".format(repr(name), ", ".join(sorted(STRATEGIES.keys())))
        ) from exc

    return factory()