def METHOD_NAME(self):
    """
    Read files via obspy.io.css.core._read_css function.
    """
    # 1
    st = _read_css(self.filename_css)
    # _format entry is not present when using low-level function
    for tr in self.st_result_css:
        tr.stats.pop('_format')
    assert st == self.st_result_css