def _df_meta_to_arr(df):
    """Check what kind of data exists in pandas columns or index. If string return as numpy array 'S' type, otherwise regular numpy array. Used when saving Brain_Data objects to hdf5.
    """
    if len(df.columns):
        if isinstance(df.columns[0], str):
            columns = df.columns.values.astype('S')
        else:
            columns = df.columns.values
    else:
        columns = []
    if len(df.index):
        if isinstance(df.index[0], str):
            index = df.index.values.astype('S')
        else:
            index = df.index.values
    else:
        index = []
    return columns, index
