docstr: internal: prepare to read PNG file
docstr_tok: ["internal",":","prepare","to","read","PNG","file"]
code: def load_prepare(self):
      """internal: prepare to read PNG file"""
  
      if self.info.get("interlace"):
          self.decoderconfig = self.decoderconfig + (1,)
  
      self.__idat = self.__prepare_idat  # used by load_read()
      ImageFile.ImageFile.load_prepare(self)
  
imports: import logging
  import re
  import struct
  import zlib
  from .None import Image, ImageFile, ImagePalette
  from ._binary import i8, i16be, i32be, o16be, o32be
  from ._util import py3
label_desc: Use image node_id 4 for calling the PngImageFile obj's underlying member method code with example usage: obj.load_prepare() without return types