code: def unpersist(self, blocking=False):
          
          self.is_cached = False
          self._jrdd.unpersist(blocking)
          return self
docs: Mark the RDD as non-persistent, and remove all blocks for it from
          memory and disk.
  
          .. versionchanged:: 3.0.0
             Added optional argument `blocking` to specify whether to block until all
             blocks are deleted.