more bugfixes

src/8_many_atoms.md

@@ -205,7 +205,8 @@ ax.set_xlabel('$ka$')
 ax.set_ylabel(r'$ω$')
 ax.set_xticks([0, pi, 2*pi])
 ax.set_xticklabels(['$0$', r'$\pi/2a$', r'$\pi/a$'])
-ax.set_yticks([], [])
+ax.set_yticks([])
+ax.set_yticklabels([])
 ax.set_xlim(-pi/8, 2*pi+.4)
 ax.set_ylim((0, dispersion_2m(0, acoustic=False) + .2))
 ax.legend(loc='lower right')