class Kramdown::Converter::Base

def highlight_code(text, lang, type, opts = {})

through the option 'syntax_highlighter'.
Highlight the given +text+ in the language +lang+ with the syntax highlighter configured 
def highlight_code(text, lang, type, opts = {})
  return nil unless @options[:syntax_highlighter]
  highlighter = ::Kramdown::Converter.syntax_highlighter(@options[:syntax_highlighter])
  if highlighter
    highlighter.call(self, text, lang, type, opts)
  else
    warning("The configured syntax highlighter #{@options[:syntax_highlighter]} is not available.")
    nil
  end
end