def isoify_dates(hash)
      hash.each_with_object({}) do |(k, v), memo|
        memo[k] = maybe_datetime_in_iso8601(v)
      end
    end
def isoify_dates(hash)
      hash.each_with_object({}) do |(k, v), memo|
        memo[k] = maybe_datetime_in_iso8601(v)
      end
    end
public: Returns a new hash with all the date values in the into iso8601
         strings