function get() {
	/* eslint-disable no-invalid-this */
	var self = this;
	if ( isNumber( this._opacity ) ) {
		return opacity;
	}
	return this._opacity;

	/**
	* Returns the opacity.
	*
	* @private
	* @returns {number} opacity
	*/
	function opacity() {
		return self._opacity; // eslint-disable-line no-underscore-dangle
	}
}
Returns a function to get an opacity.

@private
@returns {Function} opacity accessor