This demonstrate how to extend an existing backend with a custom feature for your (private) plugins.

hipchatex.plug

[Core]
Name = HipchatEx
Module = hipchatex

[Documentation]
Description = This is my customized hipchat backend.

hipchatex.py

import logging
from errbot.backends import hipchat
log = logging.getLogger('hipchatex')

class HipchatEx(hipchat.HipchatBackend):
  def __init__(self, config):
    logging.debug("yeha")
    super().__init__(config)

  def find_mention(self, name):
    """ Find the mention name of a person from his/her full name.
    """
    for user in self.conn.users:
      if user['name'] == name:
         return '@' + user['mention_name']
    return None

  @property
  def mode(self):
      return 'hipchatex'

myplugin.py

@botcmd
    def findme(self, mess, args):
        mention = self._bot.find_mention(mess.frm.resource)
        if not mention:
            return "I cannot find you"
        return "Hello " + mention