code: public List<Long> getUniverseStructures(String datasource, String filter, String ifNoneMatch) throws ApiException {
          ApiResponse<List<Long>> resp = getUniverseStructuresWithHttpInfo(datasource, filter, ifNoneMatch);
          return resp.getData();
      }
docs: List all public structures List all public structures --- This route is
  cached for up to 3600 seconds
  
  @param datasource
  The server name you would like data from (optional, default to
  tranquility)
  @param filter
  Only list public structures that have this service online
  (optional)
  @param ifNoneMatch
  ETag from a previous request. A 304 will be returned if this
  matches the current ETag (optional)
  @return List&lt;Long&gt;
  @throws ApiException
  If fail to call the API, e.g. server error or cannot
  deserialize the response body