code: def executeMethod(self, methodName, args):
      
      if not hasattr(self, methodName):
        raise Exception('Missing command method: ' + methodName)
  
      m = getattr(self, methodName)
      if not hasattr(m, '__call__'):
        raise Exception('Command: ' + methodName + ' must be callable')
  
      return m(*args)
docs: Executes a method named ``methodName`` with the specified arguments.
  
      This method is called when the user executes a command as defined in
      the node spec. It provides a perfectly reasonble implementation
      of the command mechanism. As a sub-class developer you just need to
      implement a method for each command in the node spec. Note that due to
      the command mechanism only unnamed argument are supported.
  
      :param methodName: (string) the name of the method that correspond to a
             command in the spec.
      :param args: (list) of arguments that will be passed to the method