'Apply rate function to all time series in this query.'

def Rate(self):

    if (self.time_series is None):
        raise RuntimeError('Rate    must    be    called    after    Take*().')
    if (self.sample_interval is None):
        raise RuntimeError('Normalize()    must    be    called    prior    to    Rate().')
    for time_serie in self.time_series:
        time_serie.ToDeltas()
        time_serie.Rescale((1.0 / self.sample_interval.seconds))
    return self
