```py
        >>> from datasets import load_dataset
        >>> ds = load_dataset("rotten_tomatoes", split="train", streaming=True)
        >>> next(iter(ds))
        {'text': 'the rock is destined to be the 21st century\'s new " conan " and that he\'s going to make a splash even greater than arnold schwarzenegger , jean-claud van damme or steven segal .', 'label': 1}
        >>> ds = ds.select_columns("text")
        >>> next(iter(ds))
        {'text': 'the rock is destined to be the 21st century\'s new " conan " and that he\'s going to make a splash even greater than arnold schwarzenegger , jean-claud van damme or steven segal .'}
        ```
        """
        if isinstance(column_names, str):
            column_names = [column_names]