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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 _select_theory(theories):
 """Return the most likely spacing convention given different options. Given a dictionary of convention options as keys and their occurrence as values, return the convention that occurs the most, or ``None`` if there is no clear preferred style. """

        if theories:
            values = tuple(theories.values())
            best = max(values)
            confidence = float(best) / sum(values)
            if confidence > 0.5:
                return tuple(theories.keys())[values.index(best)]