Do not import all of vtk
Do not import all of vtk

We should only import the parts that we need. In this case,
we only need vtkDataObject, so let's only import that.

Signed-off-by: Patrick Avery <743342299f279e7a8c3ff5eb40671fce3e95f13a@kitware.com>

OpenChemistry/tomviz,OpenChemistry/tomviz,OpenChemistry/tomviz,OpenChemistry/tomviz