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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 _if(cls, verb):
 """ A verb with a predicate function """

        pred = verb.predicate
        data = verb.data
        groups = set(_get_groups(verb))

        # force predicate
        if isinstance(pred, str):
            if not pred.endswith('_dtype'):
                pred = '{}_dtype'.format(pred)
            pred = getattr(pdtypes, pred)
        elif pdtypes.is_bool_dtype(np.array(pred)):
            # Turn boolean array into a predicate function
            it = iter(pred)

            def pred(col):
                return next(it)

        return [col for col in data
                if pred(data[col]) and col not in groups]