code: def as_png(self, index=None, scale_to_slice=True):
      import PIL.Image
  
      # For compatibility with older versions of PIL that did not
      # have `frombytes`:
      if hasattr(PIL.Image, "frombytes"):
          frombytes = PIL.Image.frombytes
      else:
          frombytes = PIL.Image.fromstring
  
      if index is None:
          index = len(self.storage_instances) // 2
      d = self.storage_instances[index].dicom()
      data = d.pixel_array.copy()
      if self.bits_allocated != 16:
          raise VolumeError("unsupported bits allocated")
      if self.bits_stored != 12:
          raise VolumeError("unsupported bits stored")
      data = data / 16
      if scale_to_slice:
          min = data.min()
          max = data.max()
          data = data * 255 / (max - min)
      data = data.astype(numpy.uint8)
      im = frombytes("L", (self.rows, self.columns), data.tobytes())
  
      s = BytesIO()
      im.save(s, "PNG")
      return s.getvalue()
  
imports: import contextlib
  import getpass
  import logging
  import os
  import sqlite3
  import tempfile
  import warnings
  from io import BytesIO
  from os.path import join
  import numpy
  from nibabel.optpkg import optional_package
  from .nifti1 import Nifti1Header
label_desc: Use image node_id 3 for calling the _Series obj's underlying member method code with example usage: obj.as_png(index, scale_to_slice) and returns: s