Create an empty dataframe.

        Args:
            bqstorage_client (Any):
                Ignored. Added for compatibility with RowIterator.
            dtypes (Any):
                Ignored. Added for compatibility with RowIterator.
            progress_bar_type (Any):
                Ignored. Added for compatibility with RowIterator.

        Returns:
            pandas.DataFrame:
                An empty :class:`~pandas.DataFrame`.

def to_dataframe(self, bqstorage_client=None, dtypes=None, progress_bar_type=None):
        """Create an empty dataframe.

        Args:
            bqstorage_client (Any):
                Ignored. Added for compatibility with RowIterator.
            dtypes (Any):
                Ignored. Added for compatibility with RowIterator.
            progress_bar_type (Any):
                Ignored. Added for compatibility with RowIterator.

        Returns:
            pandas.DataFrame:
                An empty :class:`~pandas.DataFrame`.
        """
        if pandas is None:
            raise ValueError(_NO_PANDAS_ERROR)
        return pandas.DataFrame()