function compare(real, expect, operator) {
	        if (operator === 'min') {
	            return real >= expect;
	        }
	        else if (operator === 'max') {
	            return real <= expect;
	        }
	        else { // Equals
	            return real === expect;
	        }
	    }
Util for merge default and theme to option
@param  {Object} option
@param  {module:echarts/model/Global} ecModel