在通過pyes獲取指定的doctype時不能通過mapping的get_doctype,只能通過get_doctypes獲取index下的所有type聘鳞,然后在自行過濾
_mapping = self._connection.indices.get_mapping(indices=index)
# _mapping.get_doctype has bug
_doctypes = _mapping.get_doctypes(index)
return doctype in dict(_doctypes)