A flat tuple of all values corresponding to `scipy_data_fitting.Fit.fixed_parameters`
        and `scipy_data_fitting.Fit.constants` after applying any prefixes.

        The values mimic the order of those lists.

def fixed_values(self):
        """
        A flat tuple of all values corresponding to `scipy_data_fitting.Fit.fixed_parameters`
        and `scipy_data_fitting.Fit.constants` after applying any prefixes.

        The values mimic the order of those lists.
        """
        values = []
        values.extend([ prefix_factor(param) * param['value'] for param in self.fixed_parameters ])
        values.extend([ prefix_factor(const) * get_constant(const['value']) for const in self.constants ])

        return tuple(values)