def resources_in(time_range:, time_attr:)
      resources.select { |r| time_range.cover?(r.send(time_attr)) }
    end
def resources_in(time_range:, time_attr:)
      resources.select { |r| time_range.cover?(r.send(time_attr)) }
    end
Finds only those resources falling within the specified time range. Any of the time
 attributes (+:modified_time+, +:at_time+, +:completed_time+, +:from_time+, +:until_time+)
 can be used for filtering.
 @param time_range [Range[Time]] the range of acceptable times (inclusive or exclusive)
 @param time_attr [Symbol] the time type to filter on: +:modified_time+, +:at_time+,
   +:completed_time+, +:from_time+ or +:until_time+
 @return [Array<Resource>] a lazy enumeration of the resources within the specified range.