This is a quiz that you can apply the pandas skills learned this lesson

your task to calculated the price of every transaction, standardized by groupings of building location since 2015

https://en.wikipedia.org/wiki/Standardization

example : 

for the first record of data, 

the building_price_hkd is 1165 and the building_location is Taikoo Shing

the mean of transaction price for Taikoo Shing is 1152.912151 and 	
the standard deviation of transaction price for Taikoo Shing is 413.899735

the first value you should return is 
(1165 - 1152.912151) / 413.899735 = 0.029205

the output should be ordered by original index value