class Jekyll::Drops::SiteDrop

def [](key) 

def [](key)
  if key != "posts" && @obj.collections.key?(key)
    @obj.collections[key].docs
  else
    super(key)
  end
end

def collections 

def collections
  @site_collections ||= @obj.collections.values.sort_by(&:label).map(&:to_liquid)
end

def config; end

return nil for `{{ site.config }}` even if --config was passed via CLI 
def config; end

def documents

additional computation of `Site#documents`.
array shouldn't thereafter change and can therefore be safely memoized to prevent
Since this method will be called after `Site#pre_render` hook, the `Site#documents`

latest state of the attribute.
`Site#documents` cannot be memoized so that `Site#docs_to_write` can access the 
def documents
  @documents ||= @obj.documents
end

def html_pages 

def html_pages
  @site_html_pages ||= @obj.pages.select do |page|
    page.html? || page.url.end_with?("/")
  end
end

def key?(key) 

def key?(key)
  (key != "posts" && @obj.collections.key?(key)) || super
end

def posts 

def posts
  @site_posts ||= @obj.posts.docs.sort { |a, b| b <=> a }
end

def related_posts

We should remove this in 4.0 and switch to `{{ post.related_posts }}`.
recent posts.
them, either through LSI if it's enabled, or through the most
`{{ site.related_posts }}` is how posts can get posts related to 
def related_posts
  return nil unless @current_document.is_a?(Jekyll::Document)
  @current_document.related_posts
end