yaml文档由分隔
---，如果任何流（例如文件）包含多个文档，则应使用
yaml.load_all函数而不是
yaml.load。编码：
import yamlstream = open("test", "r")docs = yaml.load_all(stream)for doc in docs: for k,v in doc.items(): print k, "->", v print "n",产生问题中提供的输入文件：
request -> 341570level_1 -> testlevel_2 -> NetApp, SOFS, ZFS Creationrequest -> 341569level_1 -> testlevel_2 -> NetApp, SOFS, ZFS Creationrequest -> 341568level_1 -> testlevel_2 -> NetApp, SOFS, ZFS Creation
