class Kramdown::JekyllDocument

converting all Markdown documents in a Jekyll site.
The optimization is by using the same options Hash (and its derivatives) for
a kramdown document for parsing.
A Kramdown::Document subclass meant to optimize memory usage from initializing

def initialize(source, options = {}) 

def initialize(source, options = {})
  JekyllDocument.setup(options)
  @options = JekyllDocument.options
  @root, @warnings = JekyllDocument.parser.parse(source, @options)
end

def setup(options)

rubocop:disable Naming/MemoizedInstanceVariableName

The implementation is basically the core logic in +Kramdown::Document#initialize+ 
def setup(options)
  @cache ||= {}
  # reset variables on a subsequent set up with a different options Hash
  unless @cache[:id] == options.hash
    @options = @parser = nil
    @cache[:id] = options.hash
  end
  @options ||= Options.merge(options).freeze
  @parser  ||= begin
    parser_name = (@options[:input] || "kramdown").to_s
    parser_name = parser_name[0..0].upcase + parser_name[1..-1]
    try_require("parser", parser_name)
    if Parser.const_defined?(parser_name)
      Parser.const_get(parser_name)
    else
      raise Kramdown::Error, "kramdown has no parser to handle the specified " \
                             "input format: #{@options[:input]}"
    end
  end
end

def to_html

+Kramdown::Document#method_missing+ from kramdown-2.1.0.
The implementation is basically an optimized version of core logic in

Use Kramdown::Converter::Html class to convert this document into HTML. 
def to_html
  output, warnings = Kramdown::Converter::Html.convert(@root, @options)
  @warnings.concat(warnings)
  output
end

def try_require(type, name) 

def try_require(type, name)
  require "kramdown/#{type}/#{Utils.snake_case(name)}"
rescue LoadError
  false
end