def find_distinct_item(current_list, last_list, key)
      if current_list.size == last_list.size + 1
        unique_values = current_list.map { |item| item[key] } - last_list.map { |item| item[key] }
        if unique_values.size == 1
          unique_value = unique_values[0]
          return current_list.find { |item| item[key] == unique_value }
        end
      end
      return nil
    end
def find_distinct_item(current_list, last_list, key)
      if current_list.size == last_list.size + 1
        unique_values = current_list.map { |item| item[key] } - last_list.map { |item| item[key] }
        if unique_values.size == 1
          unique_value = unique_values[0]
          return current_list.find { |item| item[key] == unique_value }
        end
      end
      return nil
    end
Determines a single, unique item (hash) by given key in the current
 list which does not appear in the last list, if any. finds nothing if
 multiple new items appear. This is useful for inspecting lists of
 disks/volumes to determine when a new item appears.

 === Parameter
 current_list(Array):: current list
 last_list(Array):: last list
 key(Symbol):: key used to uniquely identify items

 === Return
 result(Hash):: item in current list which does not appear in last list or nil