def _proc(tr, sampling_rate=10):
    """
    Basic processing including downsampling, detrend, and demean.

    :param tr: raw trace
    :param sampling_rate:
    :return tr: trace after processing
    """
    tr2 = tr.copy()
    tr2.interpolate(sampling_rate)
    tr2.detrend(type='linear')
    tr2.detrend(type='demean')
    return tr2
