# Return the set of all elements `f` that have an edge from `f` to `element`.
	# Since the POSet is reflexive, element is included in the set.
	#
	# ~~~~
	# var pos = new POSet[String]
	# pos.add_chain(["A", "B", "C", "D"])
	# assert pos["C"].smallers.has_exactly(["A", "B", "C"])
	# ~~~~
	fun smallers: Collection[E]
	do
		return self.froms
	end