<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def parameters(self):
 """ Return the model parameters. """


        try:
            return self._parameters

        except AttributeError:
            None

        parameters = []
        parameters.extend(self.grid_points.dtype.names)

        model_configuration = self._configuration.get("model", {})

        # Continuum
        # Note: continuum cannot just be 'True', it should be a dictionary
        n = len(parameters)
        continuum_config = model_configuration.get("continuum", False)
        if continuum_config is not False:
            if not isinstance(continuum_config, dict):
                raise TypeError("incorrect continuum type")
            for name in set(self.channel_names).intersection(continuum_config):
                degree = continuum_config[name]
                if degree is False:
                    continue

                # Note: N_coefficients = degree + 1
                # Example: degree = 3: a^3 + b^2 + c^1 + d 
                parameters.extend(["continuum_{0}_{1}".format(name, n) \
                    for n in range(degree + 1)])

        # Redshift
        parameters.extend(channel_parameters("z", self.channel_names,
            model_configuration.get("redshift", False)))

        # Spectral resolution
        resolution_parameters = channel_parameters(
            "resolution", self.channel_names,
            model_configuration.get("spectral_resolution", False))
        parameters.extend(resolution_parameters)

        # Underestimated variance
        parameters.extend(channel_parameters(
            "ln_f", self.channel_names,
            model_configuration.get("underestimated_variance", False)))

        # Outlier pixels
        if model_configuration.get("outlier_pixels", False):
            parameters.extend(["Po", "Vo"])

        assert len(parameters) == len(set(parameters)), "Duplicate parameters!"

        self._resolution_parameters = resolution_parameters
        self._parameters = tuple(parameters)

        return self._parameters