# Get option as a MEntity
	#
	# Lookup first by `MEntity::full_name` then by `MEntity::name`.
	# Return `null` if the mentity name does not exist or return a conflict.
	private fun opt_mentity(model: Model, key: String): nullable MEntity do
		var value = opt_string(key)
		if value == null or value.is_empty then return null

		var mentity = model.mentity_by_full_name(value)
		if mentity != null then return mentity

		var mentities = model.mentities_by_name(value)
		if mentities.is_empty or mentities.length > 1 then return null
		return mentities.first
	end