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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def previous_open(self, dt):
 """ Given a dt, returns the previous open. Parameters dt: pd.Timestamp The dt for which to get the previous open. Returns ------- pd.Timestamp The UTC imestamp of the previous open. """

        idx = previous_divider_idx(self.market_opens_nanos, dt.value)
        return pd.Timestamp(self.market_opens_nanos[idx], tz=UTC)