Selection by QUERY extraction fails at providing a vtkSignedChar array
extract_selection.py fails at providing a vtkSignedCharArray, as one can check when using vtkConvertSelection.cxx, gdb would give the following :
(gdb) print insidedness
$13 = (vtkSignedCharArray *) 0x0
(gdb) print extracted->GetCellData()->GetAbstractArray("vtkInsidedness")->GetClassName()
$14 = 0x7fffe0c484d3 "vtkCharArray"
It is due to numpy_selection.py converting the same numpy type to both array type.