David Gobbi authored Aug 31, 2017 and Ben Boeckel committed Jan 08, 2019

When the VTK Python extension modules are loaded more than once
(e.g. by multiple Python interpreters in the same process), we
must ignore any PyTypeObjects except for the ones from the first
load.  This fixes crashes that started occurring when we moved
the PyTypeObjects from the shared PythonD libraries into the
Python modules themselves.