# Return the last value
	#
	# https://docs.mongodb.com/manual/reference/operator/aggregation/last/
	#
	# ~~~json
	# { $last: <expression> }
	# ~~~
	#
	# Returns the value that results from applying an expression to the last
	# document in a group of documents that share the same group by key.
	#
	# Only meaningful when documents are in a defined order.
	fun last(field: String, expression: Serializable): MongoGroup do
		return acc("last", field, expression)
	end