def cities(ids, options = {})
      if ids.length > SeveralCitiesClassMethods::LOCATIONS_LIMIT
        raise LocationsLimitExceeded
      end

      url = 'http://api.openweathermap.org/data/2.5/group'
      ids = encode_array ids
      new(options.merge(id: ids)).retrieve url
    end
def cities(ids, options = {})
      if ids.length > SeveralCitiesClassMethods::LOCATIONS_LIMIT
        raise LocationsLimitExceeded
      end

      url = 'http://api.openweathermap.org/data/2.5/group'
      ids = encode_array ids
      new(options.merge(id: ids)).retrieve url
    end
City Ids, an array of integer values. Eg, [2172797, 524901]
 Usage: OpenWeather::Current.cities([2172797, 524901])

 Note that every ID in the array counts as an API call.
 A LocationsLimitExceeded error is raised if the API limit is exceeded.