Why does vim-ipython preview window close with <esc> in code buffer window?

I have noticed that when I am editing a file and the vim-ipython window is open, and, in the source code, I hit `<ESC>` (moving from insert to normal mode), that the vim-ipython preview window closes.  Is there a way to change this behavior? I would prefer that the vim-ipython preview window stay open unless I explicitly close it.

Thanks!

Jose