docs: def set_plot_CO_mass(self,fig=3123,xaxis='mass',linestyle=['-'],marker=['o'],color=['r'],age_years=True,sparsity=500,markersparsity=200,withoutZlabel=False,t0_model=[]):
  		
  		'''
  			PLots C/O surface number fraction
  		'''
  
  		if len(t0_model)==0:
  			t0_model = len(self.runs_H5_surf)*[0]
  
  		plt.figure(fig)
                  for i in range(len(self.runs_H5_surf)):
                          sefiles=se(self.runs_H5_surf[i])
  			cycles=range(int(sefiles.se.cycles[0]),int(sefiles.se.cycles[-1]),sparsity)
  			mini=sefiles.get("mini")
  			zini=sefiles.get("zini")
  			label=str(mini)+'$M_{\odot}$, Z='+str(zini)
  			if xaxis=='cycles':
  				x=cycles
  			if xaxis=='age':
  				x=sefiles.get(cycles,'age')
                          	if age_years==True:
                                  	x=np.array(x)*sefiles.get('age_unit')/(365*24*3600)
  				x = x - x[t0_model[i]]
  			if xaxis=='mass':
  				x=sefiles.get(cycles,'mass')
  			x=x[t0_model[i]:]
  			c12=sefiles.get(cycles,'C-12')[t0_model[i]:]
  			o16=sefiles.get(cycles,'O-16')[t0_model[i]:]
  			if withoutZlabel==True:
  				plt.plot(x,4./3.*np.array(c12)/np.array(o16),label=label.split(',')[0],marker=marker[i],linestyle=linestyle[i],markevery=markersparsity,color=color[i])
  
  			else:
  				plt.plot(x,4./3.*np.array(c12)/np.array(o16),label=label,marker=marker[i],linestyle=linestyle[i],markevery=markersparsity,color=color[i])
  			if xaxis=='mass':
  				plt.xlim(7,0.5)
  				#plt.gca().invert_xaxis()	
  	                        plt.xlabel('$M/M_{\odot}$',fontsize=18)
  	
                          plt.ylabel('C/O Ratio', fontsize=18)
  			plt.legend(loc=1)