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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 daily_returns(self, start, end=None):
 """Returns the daily returns for the given period. Parameters start : datetime The inclusive starting session label. end : datetime, optional The inclusive ending session label. If not provided, treat ``start`` as a scalar key. Returns ------- returns : pd.Series or float The returns in the given period. The index will be the trading calendar in the range [start, end]. If just ``start`` is provided, return the scalar value on that day. """

        if end is None:
            return self._daily_returns[start]

        return self._daily_returns[start:end]