A jekyll filter to sort out and return only the wp:post_meta keys and values

wp_metadata_filter.rb

module Jekyll
  module WPmetadata
    def wpmeta(input)
      standard_post = [
        "output",
        "content",
        "relative_path",
        "path",
        "url",
        "collection",
        "next",
        "previous",
        "id",
        "draft",
        "categories",
        "layout",
        "title",
        "tags",
        "slug",
        "ext",
        "date",
        "excerpt",
        "author",
        "permalink"
      ]
      postdata = input.delete_if {|x| standard_post.index(x)}
    end
  end
end

Liquid::Template.register_filter(Jekyll::WPmetadata)
# use in a template like this {{ post | wpmeta }}
# returns a hash like { "key" => "value" } for any
# keys in the post hash that are not in the array
# of standard post values (lns 4-24).