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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def flush(self, preserve=None):
 """ Delete the cache for this dataset. Optionally preserve a region. Helpful when working with overlaping volumes. Warning: the preserve option is not multi-process safe. You're liable to end up deleting the entire cache. Optional: preserve (Bbox: None):
 Preserve chunks located partially or entirely within this bounding box. Return: void """

    if not os.path.exists(self.path):
      return

    if preserve is None:
      shutil.rmtree(self.path)
      return

    for mip in self.vol.available_mips:
      preserve_mip = self.vol.slices_from_global_coords(preserve)
      preserve_mip = Bbox.from_slices(preserve_mip)

      mip_path = os.path.join(self.path, self.vol.mip_key(mip))
      if not os.path.exists(mip_path):
        continue

      for filename in os.listdir(mip_path):
        bbox = Bbox.from_filename(filename)
        if not Bbox.intersects(preserve_mip, bbox):
          os.remove(os.path.join(mip_path, filename))