code: def no_vtk():
      """Checks if VTK is installed and the python wrapper is functional"""
      global _vtk_version
      return _vtk_version is None
  
file_path: nipype/nipype/interfaces/vtkbase.py
imports: import os
  from ..None import logging
label_desc: Use image node_id 2 for calling a global function with example usage: no_vtk() and returns: unknown