Traceback (most recent call last):
  File "C:\Anaconda3\lib\threading.py", line 914, in _bootstrap_inner
    self.run()
  File "C:\Anaconda3\lib\threading.py", line 862, in run
    self._target(*self._args, **self._kwargs)
  File "C:\levproject\tests\pass_to_source\server.py", line 67, in update_data
    ses._document.select_one({'name':'source'}).data = {'dat':pd.read_csv('data.csv').iloc[0].tolist()}
  File "C:\Anaconda3\lib\site-packages\bokeh\core\properties.py", line 716, in __setattr__
    super(HasProps, self).__setattr__(name, value)
  File "C:\Anaconda3\lib\site-packages\bokeh\core\properties.py", line 458, in __set__
    self._real_set(obj, old, value)
  File "C:\Anaconda3\lib\site-packages\bokeh\core\properties.py", line 448, in _real_set
    self._trigger(obj, old, value, hint)
  File "C:\Anaconda3\lib\site-packages\bokeh\core\properties.py", line 397, in _trigger
    obj.trigger(self.name, old, value, hint)
  File "C:\Anaconda3\lib\site-packages\bokeh\model.py", line 121, in trigger
    super(Model, self).trigger(attr, old, new, hint)
  File "C:\Anaconda3\lib\site-packages\bokeh\util\callback_manager.py", line 104, in trigger
    self._document._notify_change(self, attr, old, new, hint)
  File "C:\Anaconda3\lib\site-packages\bokeh\document.py", line 611, in _notify_change
    self._trigger_on_change(ModelChangedEvent(self, model, attr, old, new, serializable_new, hint))
  File "C:\Anaconda3\lib\site-packages\bokeh\document.py", line 595, in _trigger_on_change
    self._with_self_as_curdoc(invoke_callbacks)
  File "C:\Anaconda3\lib\site-packages\bokeh\document.py", line 577, in _with_self_as_curdoc
    return f()
  File "C:\Anaconda3\lib\site-packages\bokeh\document.py", line 594, in invoke_callbacks
    cb(event)
  File "C:\Anaconda3\lib\site-packages\bokeh\document.py", line 558, in <lambda>
    self._callbacks[receiver] = lambda event: event.dispatch(receiver)
  File "C:\Anaconda3\lib\site-packages\bokeh\document.py", line 112, in dispatch
    super(ModelChangedEvent, self).dispatch(receiver)
  File "C:\Anaconda3\lib\site-packages\bokeh\document.py", line 99, in dispatch
    receiver._document_patched(self)
  File "C:\Anaconda3\lib\site-packages\bokeh\server\session.py", line 172, in _document_patched
    raise RuntimeError("_pending_writes should be non-None when we have a document lock, and we should have the lock when the document changes")
RuntimeError: _pending_writes should be non-None when we have a document lock, and we should have the lock when the document changes