code: def topng(self, path, prefix='image', overwrite=False):
          
          from thunder.images.writers import topng
          # TODO add back colormap and vmin/vmax
          topng(self, path, prefix=prefix, overwrite=overwrite)
docs: Write 2d images as PNG files.
  
          Files will be written into a newly-created directory.
          Three-dimensional data will be treated as RGB channels.
  
          Parameters
          ----------
          path : string
              Path to output directory, must be one level below an existing directory.
  
          prefix : string
              String to prepend to filenames.
  
          overwrite : bool
              If true, the directory given by path will first be deleted if it exists.