code: def py2js_tickformatter(formatter, msg=''):
      
      try:
          from flexx.pyscript import py2js
      except ImportError:
          param.main.param.warning(
              msg+'Ensure Flexx is installed ("conda install -c bokeh flexx" '
              'or "pip install flexx")')
          return
      try:
          jscode = py2js(formatter, 'formatter')
      except Exception as e:
          error = 'Pyscript raised an error: {0}'.format(e)
          error = error.replace('%', '%%')
          param.main.param.warning(msg+error)
          return
  
      args = _getargspec(formatter).args
      arg_define = 'var %s = tick;' % args[0] if args else ''
      return_js = 'return formatter();\n'
      jsfunc = '\n'.join([arg_define, jscode, return_js])
      match = re.search('(formatter \= function \(.*\))', jsfunc )
      return jsfunc[:match.start()] + 'formatter = function ()' + jsfunc[match.end():]
docs: Uses flexx.pyscript to compile a python tick formatter to JS code