code: def Vindex(x):
      if isinstance(x, funsor.Funsor):
          return x
      return _Vindex(x)
  
imports: import warnings
  import pytest
  import funsor
  from funsor.testing import xfail_param
  from funsor.util import get_backend
label_desc: Use image node_id 1 for calling a global function with example usage: Vindex(x) and returns: _Vindex, x