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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 evtrack(self,m,feh=0.0,minage=None,maxage=None,dage=0.02, return_df=True):
 """ Returns evolution track for a single initial mass and feh. :param m: Initial mass of desired evolution track. :param feh: (optional) Metallicity of desired track. Default = 0.0 (solar) :param minage, maxage: (optional) Minimum and maximum log(age) of desired track. Will default to min and max age of model isochrones. :param dage: (optional) Spacing in log(age) at which to evaluate models. Default = 0.02 :param return_df: (optional) Whether to return a ``DataFrame`` or dicionary. Default is ``True``. :return: Either a :class:`pandas.DataFrame` or dictionary representing the evolution track---fixed mass, sampled at chosen range of ages. """

        if minage is None:
            minage = self.minage
        if maxage is None:
            maxage = self.maxage
        ages = np.arange(minage,maxage,dage)
        Ms = self.mass(m,ages,feh)
        Rs = self.radius(m,ages,feh)
        logLs = self.logL(m,ages,feh)
        loggs = self.logg(m,ages,feh)
        Teffs = self.Teff(m,ages,feh)
        mags = {band:self.mag[band](m,ages,feh) for band in self.bands}

        props = {'age':ages,'mass':Ms,'radius':Rs,'logL':logLs,
                'logg':loggs, 'Teff':Teffs, 'mag':mags}

        if not return_df:
            return props
        else:
            d = {}
            for key in props.keys():
                if key=='mag':
                    for m in props['mag'].keys():
                        d['{}_mag'.format(m)] = props['mag'][m]
                else:
                    d[key] = props[key]
            try:
                df = pd.DataFrame(d)
            except ValueError:
                df = pd.DataFrame(d, index=[0])
            return df