new_contents: __all__ = ['emoji']
  
  EMOJI = r':[a-z0-9-]+:'
  
  
  def parse_emoji(inline, m, state):
      text = m.group(0)
      state.append_token({
          'type': 'emoji',
          'raw': text,
      })
      return m.end()
  
  
  def emoji(md):
      md.inline.register_rule('emoji', EMOJI, parse_emoji, before='link')
  
subject: Add emoji plugin