# Apply unwind
	#
	# https://docs.mongodb.com/manual/reference/operator/aggregation/unwind/
	#
	# Deconstructs an array field from the input documents to output a document
	# for each element.
	# Each output document is the input document with the value of the array
	# field replaced by the element.
	#
	# ~~~json
	# { $unwind: <field path> }
	# ~~~
	fun unwind(path: String): MongoPipeline do return add_stage("unwind", path)