How to use the nexusformat.nexus.NXparameters function in nexusformat

def save_fit(self):
        """Saves fit results to an NXentry"""
        self.read_parameters()
        group = NXprocess()
        group['data'] = self.data
        for f in self.functions:
            group[f.name] = self.get_model(f)
            parameters = NXparameters()
            for p in f.parameters:
                parameters[p.name] = NXfield(p.value, error=p.stderr, 
                                             initial_value=p.init_value,
                                             min=str(p.min), max=str(p.max))
            group[f.name].insert(parameters)
        if self.fit is not None:
            group['program'] = 'lmfit'
            group['version'] = lmfit.__version__
            group['title'] = 'Fit Results'
            group['fit'] = self.get_model()
            fit = NXparameters()
            fit.nfev = self.fit.result.nfev
            fit.chisq = self.fit.result.chisqr
            fit.redchi = self.fit.result.redchi
            fit.message = self.fit.result.message
            group['statistics'] = fit

group = NXprocess()
        group['data'] = self.data
        for f in self.functions:
            group[f.name] = self.get_model(f)
            parameters = NXparameters()
            for p in f.parameters:
                parameters[p.name] = NXfield(p.value, error=p.stderr, 
                                             initial_value=p.init_value,
                                             min=str(p.min), max=str(p.max))
            group[f.name].insert(parameters)
        if self.fit is not None:
            group['program'] = 'lmfit'
            group['version'] = lmfit.__version__
            group['title'] = 'Fit Results'
            group['fit'] = self.get_model()
            fit = NXparameters()
            fit.nfev = self.fit.result.nfev
            fit.chisq = self.fit.result.chisqr
            fit.redchi = self.fit.result.redchi
            fit.message = self.fit.result.message
            group['statistics'] = fit
            group.note = NXnote(self.fit.result.message,
                ('Chi^2 = %s\n' % self.fit.result.chisqr +
                 'Reduced Chi^2 = %s\n' % self.fit.result.redchi +

                 'No. of Function Evaluations = %s\n' % self.fit.result.nfev +
                 'No. of Variables = %s\n' % self.fit.result.nvarys +
                 'No. of Data Points = %s\n' % self.fit.result.ndata +
                 'No. of Degrees of Freedom = %s\n' % self.fit.result.nfree +
                 '%s' % self.fit.fit_report()))
        else:
            group['title'] = 'Fit Model'