Expect the daily sums of the given column to be close to the average sums calculated 4 weeks back.

This metric expects daily sums of the given column, to be close to the average sums calculated 4 weeks back,
respective to the specific day of the week.
The expectation fails if the difference in percentage ((current_sum - average_sum) / average_sum) is more than the
threshold given by user (default value is 25%).
The threshold parameter should be given in fraction and not percent, i.e. for 25% define threshold = 0.25.

Keyword args:

• • threshold (float; default = 0.25): threshold of difference between current and past weeks over which expectation fails
• • weeks_back (int; default = 4): how many weeks back to compare the current metric with