@staticmethod
def _wrap_columns(columns):
    """Transform pandas.MultiIndex into pandas.Index for the pandas.DataFrame columns.

        Notes:
            the libsonata.ElementsReader.get() returns tuple as columns for the data. For the
            soma reports it means: pandas.MultiIndex([(0, 0), (1, 0), ..., (last_node_id, 0)]).
            So we convert this into pandas.Index([0,1,..., last_node_id]).
        """
    return columns.levels[0]
