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  "body": "\n## Proof\n\nApply the transformation rules to $\\phi$ to produce an equivalent formula containing no relations, special classes, or operations. This formula satisfies the hypothesis of the class existence theorem. Therefore, for all $Y_1, \\dots, Y_m,$ there is a unique class $A$ of $n$-tuples satisfying\n\n$$\\forall x_1 \\cdots \\,\\forall x_n [(x_1, \\dots, x_n) \\in A \\iff \\phi(x_1, \\dots, x_n, Y_1, \\dots, Y_m)].$$\n",
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