_disabledReason_controlInside(row) {
        let g = this.gates[row];
        for (let j = 1; j < g.height && row + j < this.gates.length; j++) {
            if (this.gates[row + j] !== undefined && this.gates[row + j].isControl()) {
                return "control\ninside";
            }
        }
        return undefined;
    }
@param {!int} row
@returns {undefined|!string}
@private