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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 write_psts(self,prefix,existing_jco=None,noptmax=None):
 """ write parameter and optionally observation realizations to a series of pest control files Parameters prefix: str pest control file prefix existing_jco: str filename of an existing jacobian matrix to add to the pest++ options in the control file. This is useful for NSMC since this jco can be used to get the first set of parameter upgrades for free! Needs to be the path the jco file as seen from the location where pest++ will be run noptmax: int value of NOPTMAX to set in new pest control files Example ------- """

        self.log("writing realized pest control files")
        # get a copy of the pest control file
        pst = self.pst.get(par_names=self.pst.par_names,obs_names=self.pst.obs_names)

        if noptmax is not None:
            pst.control_data.noptmax = noptmax
            pst.control_data.noptmax = noptmax

        if existing_jco is not None:
            pst.pestpp_options["BASE_JACOBIAN"] = existing_jco

        # set the indices
        pst.parameter_data.index = pst.parameter_data.parnme
        pst.observation_data.index = pst.observation_data.obsnme

        if self.parensemble.istransformed:
            par_en = self.parensemble._back_transform(inplace=False)
        else:
            par_en = self.parensemble

        for i in range(self.num_reals):
            pst_name = prefix + "{0:d}.pst".format(i)
            self.log("writing realized pest control file " + pst_name)
            pst.parameter_data.loc[par_en.columns,"parval1"] = par_en.iloc[i, :].T

            # reset the regularization
            #if pst.control_data.pestmode == "regularization":
                #pst.zero_order_tikhonov(parbounds=True)
                #zero_order_tikhonov(pst,parbounds=True)
            # add the obs noise realization if needed
            if self.obsensemble.shape[0] == self.num_reals:
                pst.observation_data.loc[self.obsensemble.columns,"obsval"] = \
                    self.obsensemble.iloc[i, :].T

            # write
            pst.write(pst_name)
            self.log("writing realized pest control file " + pst_name)
        self.log("writing realized pest control files")