code: def ref(self):
          ''' A Bokeh protocol "reference" to this model, i.e. a dict of the
          form:
  
          .. code-block:: python
  
              {
                  'type' : << view model name >>
                  'id'   : << unique model id >>
              }
  
          Additionally there may be a `subtype` field if this model is a subtype.
  
          '''
          if "__subtype__" in self.__class__.__dict__:
              return {
                  'type'    : self.__view_model__,
                  'subtype' : self.__subtype__,
                  'id'      : self.id,
              }
          else:
              return {
                  'type' : self.__view_model__,
                  'id'   : self.id,
              f ref(self):
          ''' A Bokeh protocol "reference" to this model, i.e. a dict of the
          form:
  
          .. code-block:: python
  
              {
                  'type' : << view model name >>
                  'id'   : << unique model id >>
              }
  
          Additionally there may be a `subtype` field if this model is a subtype.
  
          '''
          if "__subtype__" in self.__class__.__dict__:
              return {
                  'type'    : self.__view_model__,
                  'subtype' : self.__subtype__,
                  'id'      : self.id,
              }
          else:
              return {
                  'type' : self.__view_model__,
                  'id'   : self.id,
              }
docs: A Bokeh protocol "reference" to this model, i.e. a dict of the
          form:
  
          .. code-block:: python
  
              {
                  'type' : << view model name >>
                  'id'   : << unique model id >>
              }
  
          Additionally there may be a `subtype` field if this model is a subtype.