在urllib.request python 3中设置标题

Question

下面的代码中 body （指？）的含义是什么？

headers = ['Content-length']=str(len(bytes(body, 'utf-8')))

return urllib.request.Request(theurl, bytes(body, 'utf-8'), headers)

Sourse：BadStatusLine exception raised when returning reply from server in Python 3