code: def make_chunk(chunk_type, chunk_data):
  	
  	out = struct.pack("!I", len(chunk_data))
  	chunk_data = chunk_type.encode("latin-1") + chunk_data
  	out += chunk_data + struct.pack("!I", binascii.crc32(chunk_data) & 0xffffffff)
  	return out
docs: Create a raw chunk by composing chunk type and data. It
  	calculates chunk length and CRC for you.
  
  	:arg str chunk_type: PNG chunk type.
  	:arg bytes chunk_data: PNG chunk data, **excluding chunk length, type, and CRC**.
  	:rtype: bytes