text: #!/usr/bin/env python
  
  from okdataset.clist import ChainableList
  from okdataset.context import Context
  from okdataset.logger import Logger
  
  logger = Logger("map from existing example")
  
  context = Context()
  logger.info("Building dataset from existing")
  ds = context.dataSet(label="big list", fromExisting=True)
  
  logger.info("Calling map")
  ds.map(lambda x: x * 2)
  ds.map(lambda x: x + 3)
  ds.compute()
  logger.info("All done!")
  
  