IPython --existing doesn't forget previous invocation

[PetraOleum]

As mentioned in the Readme, running :IPython twice causes the old connection to be forgotten. However if the kernel has been created elsewhere using jupyter console (e.g. in another nvim tab) and then you run :IPython --existing twice and start sending instructions to it, they start showing up twice:

nvim-ipy: Jupyter shell for Neovim
Jupyter 4.7.0-final
language: python 3.8.6


In[1]: 1+1
Out[1]: 2

Jupyter 4.7.0-final
language: python 3.8.6

In[2]: 1+1

In[2]: 1+1
Out[2]: 2
Out[2]: 2

Jupyter 4.7.0-final
language: python 3.8.6

In[3]: 1+1

In[3]: 1+1
Out[3]: 2
Out[3]: 2

In[3]: 1+1
Out[3]: 2

(And so on, as :IPython --existing is invoked more and more times.)