static fromWireSwap(numWires, swapWire1, swapWire2) {
        let bitSwap = n => {
            let m1 = 1 << swapWire1;
            let m2 = 1 << swapWire2;
            let s = n & ~(m1 | m2);
            if ((n & m1) !== 0) { s |= m2; }
            if ((n & m2) !== 0) { s |= m1; }
            return s;
        };
        return Matrix.generateTransition(1<<numWires, bitSwap);
    }
Returns a matrix for an n-wire circuit that swaps wires i and j.
@param {!int} numWires
@param {!int} swapWire1
@param {!int} swapWire2