At the conclusion of Neilah, at the final moments of Yom Kippur, we have a dramatic "Declaration of Faith:" The Chazan says Sh'ma Yisrael, & we repeat it; he says Baruch Shem K'vod Malchuto 3 times & we repeat it; & he then says "Hashem Hu Ha-Elokim" 7 times & we repeat it. What is the meaning of all this?