Rstudio 中的簿记文件的有效 YAML 标头是什么样的

Question

我是 bookdown 包的新手，遇到了这个错误；

"Error in yaml::yaml.load(..., eval.expr = TRUE) : 
  Parser error: while parsing a block mapping at line 1, column 1 did not find expected key at line 2, column 14
Calls: <Anonymous> ... setNames -> resolve -> <Anonymous> -> yaml_load -> <Anonymous>
Execution halted"

我已将我的标头放入 YAML 验证器中，它似乎是一个有效的标头。这是我的标题；

title: "A Baseline Examination of the Stream Health"
author: "Authors"
date: "`r Sys.Date()`"
site: bookdown::bookdown_site
output: bookdown::gitbook
documentclass: book
bibliography:
  - book.bib
  - packages.bib
biblio-style: apalike
link-citations: yes
github-repo: rstudio/bookdown-demo
description: "Discription"

我尝试将 YAML 标头放入 YAML 验证器中，这表明 YAML 标头有效。