code: def png_size(self, index=None, scale_to_slice=True):
      return len(
          self.as_png(index=index, scale_to_slice=scale_to_slice)
      )
  
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 4 for calling the _Series obj's underlying member method code with example usage: obj.png_size(index, scale_to_slice) and returns: len