code: def _get_crc32(self, filename):
          
          buffer = self.zip.read(filename)
          if filename not in self.files_crc32:
              self.files_crc32[filename] = crc32(buffer)
              if self.files_crc32[filename] != self.zip.getinfo(filename).CRC:
                  log.error("File '{}' has different CRC32 after unpacking! "
                            "Declared: {:08x}, Calculated: {:08x}".format(filename,
                                                                          self.zip.getinfo(filename).CRC,
                                                                          self.files_crc32[filename]))
          return buffer
docs: Calculates and compares the CRC32 and returns the raw buffer.
  
          The CRC32 is added to `files_crc32` dictionary, if not present.
  
          :param filename: filename inside the zipfile
          :rtype: bytes