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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 set_str2(s, base, context=None):
 """ Convert the string ``s`` in base ``base`` to a BigFloat instance, rounding according to the current context. Raise ValueError if ``s`` doesn't represent a valid string in the given base. """

    return _apply_function_in_current_context(
        BigFloat,
        _set_from_whole_string,
        (s, base),
        context,
    )