Compute the stellar mass (Msun; average per star). PDF comes
        from IMF, but weight by actual stellar mass.

        Parameters:
        -----------
        mass_min : Minimum mass to integrate the IMF
        steps    : Number of steps to sample the isochrone

        Returns:
        --------
        mass     : Stellar mass [Msun]

def stellar_mass(self, mass_min=0.1, steps=10000):
        """
        Compute the stellar mass (Msun; average per star). PDF comes
        from IMF, but weight by actual stellar mass.

        Parameters:
        -----------
        mass_min : Minimum mass to integrate the IMF
        steps    : Number of steps to sample the isochrone

        Returns:
        --------
        mass     : Stellar mass [Msun]
        """
        mass_max = self.mass_init_upper_bound
            
        d_log_mass = (np.log10(mass_max) - np.log10(mass_min)) / float(steps)
        log_mass = np.linspace(np.log10(mass_min), np.log10(mass_max), steps)
        mass = 10.**log_mass

        if mass_min < np.min(self.mass_init):
            mass_act_interpolation = scipy.interpolate.interp1d(np.insert(self.mass_init, 0, mass_min),
                                                                np.insert(self.mass_act, 0, mass_min))
        else:
           mass_act_interpolation = scipy.interpolate.interp1d(self.mass_init, self.mass_act) 

        mass_act = mass_act_interpolation(mass)
        return np.sum(mass_act * d_log_mass * self.imf.pdf(mass, log_mode=True))