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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 generate_qinit_from_past_qout(self, qinit_file, time_index=-1, out_datetime=None):
 """ Generate qinit from a RAPID qout file Parameters qinit_file: str Path to output qinit_file. time_index: int, optional Index of simulation to generate initial flow file. Default is the last index. out_datetime: :obj:`datetime.datetime`, optional Datetime object containing time of initialization. Example: .. code:: python from RAPIDpy import RAPID rapid_manager = RAPID( Qout_file='/output_mississippi-nfie/Qout_k2v1_2005to2009.nc', rapid_connect_file='/input_mississippi_nfie/rapid_connect.csv' ) rapid_manager.generate_qinit_from_past_qout( qinit_file='/input_mississippi_nfie/Qinit_2008_flood.csv', time_index=10162 ) """

        if not self.Qout_file or not os.path.exists(self.Qout_file):
            log('Missing Qout_file. '
                'Please set before running this function ...',
                "ERROR")

        if not self.rapid_connect_file or not self.rapid_connect_file:
            log('Missing rapid_connect file. '
                'Please set before running this function ...',
                "ERROR")

        log("Generating qinit file from qout file ...",
            "INFO")
        # get information from dataset
        with xarray.open_dataset(self.Qout_file) as qds:
            rivid_array = qds.rivid.values
            if out_datetime is None:
                streamflow_values = qds.isel(time=time_index).Qout.values
            else:
                streamflow_values = qds.sel(time=str(out_datetime)).Qout.values

        log("Reordering data ...",
            "INFO")

        stream_id_array = np.loadtxt(self.rapid_connect_file,
                                     ndmin=1, delimiter=",",
                                     usecols=(0,), dtype=int)
        init_flows_array = np.zeros(stream_id_array.size)
        for riv_bas_index, riv_bas_id in enumerate(rivid_array):
            try:
                data_index = np.where(stream_id_array == riv_bas_id)[0][0]
                init_flows_array[data_index] = streamflow_values[riv_bas_index]
            except IndexError:
                log('riv bas id {0} not found in connectivity list.'
                    .format(riv_bas_id),
                    "WARNING")

        log("Writing to file ...",
            "INFO")
        with open_csv(qinit_file, 'w') as qinit_out:
            for init_flow in init_flows_array:
                qinit_out.write('{0}\n'.format(init_flow))

        self.Qinit_file = qinit_file
        self.BS_opt_Qinit = True
        log("Initialization Complete!",
            "INFO")