markAsControlExpecting(bit, guaranteedClassical=false) {
        this.gate._controlBit = bit;
        this.gate.isControlWireSource = true;
        this.gate.interestedInControls = false;
        this.gate._isClassicalControl = guaranteedClassical;
        return this;
    }
Sets meta-properties to indicate a gate is a control.
@param {!boolean|!string} bit: Whether gate is a control (True), anti-control (False), or parity control
    ("parity"). Use before/after operations for flexibility.
@param {!boolean} guaranteedClassical Whether or not the control can be used to control permutations of classical
    wires, even if placed on a coherent wire.
@returns {!GateBuilder}