function AngleAxis(scale, angleExtent) {

    angleExtent = angleExtent || [0, 360];

    Axis.call(this, 'angle', scale, angleExtent);

    /**
     * Axis type
     *  - 'category'
     *  - 'value'
     *  - 'time'
     *  - 'log'
     * @type {string}
     */
    this.type = 'category';
}
@param {string} [dim] 'radius' or 'angle' or 'auto' or null/undefined
@return {Object} {baseAxes: [], otherAxes: []}