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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 _at(cls, verb):
 """ A verb with a select text match """

        # Named (listed) columns are always included
        columns = cls.select(verb)
        final_columns_set = set(cls.select(verb))
        groups_set = set(_get_groups(verb))
        final_columns_set -= groups_set - set(verb.names)

        def pred(col):
            if col not in verb.data:
                raise KeyError(
                    "Unknown column name, {!r}".format(col))
            return col in final_columns_set

        return [col for col in columns if pred(col)]