code: public java.util.Map<String, java.util.List<java.util.List<Long>>> getItems() {
          return items;
      }
docs: <p>
  The usage data, as daily logs of used and remaining quotas, over the specified time interval indexed over the API
  keys in a usage plan. For example,
  <code>{..., "values" : { "{api_key}" : [ [0, 100], [10, 90], [100, 10]]}</code>, where <code>{api_key}</code>
  stands for an API key value and the daily log entry is of the format <code>[used quota, remaining quota]</code>.
  </p>
  
  @return The usage data, as daily logs of used and remaining quotas, over the specified time interval indexed over
  the API keys in a usage plan. For example,
  <code>{..., "values" : { "{api_key}" : [ [0, 100], [10, 90], [100, 10]]}</code>, where
  <code>{api_key}</code> stands for an API key value and the daily log entry is of the format
  <code>[used quota, remaining quota]</code>.