def DAY_OF_MONTH(expression):
return {'<STR_LIT>': expression}<EOL>
Returns the day of the month for a date as a number between 1 and 31.
See https://docs.mongodb.com/manual/reference/operator/aggregation/dayOfMonth/
for more details
:param expression: expression or variable of a Date, a Timestamp, or an ObjectID
:return: Aggregation operator