new_contents: # -*- coding: utf-8 -*-
  from __future__ import print_function, division, absolute_import
  import warnings
  
  try:
      import pygments
  except ImportError, e:
      warnings.warn("Pygments not installed")
      pygments = None
  else:
      from pygments import highlight
      from pygments.lexers import PythonLexer, LlvmLexer
      from pygments.formatters import HtmlFormatter, TerminalFormatter
  
  # ______________________________________________________________________
  
  lexers = {
      "python": PythonLexer,
      "llvm": LlvmLexer,
  }
  
  formatters = {
      "html": HtmlFormatter,
      "console": TerminalFormatter,
  }
  
  def lex_source(code, lexer="python", output='html', inline_css=True):
      Lexer = lexers[lexer]
      Formatter = formatters[output]
      return highlight(code, Lexer(), Formatter(noclasses=inline_css))
subject: Add a lexing module