code: def _variable_is_none(var):
      return isinstance(var, Constant) and var.data is None
  
imports: import numpy
  from pytensor.gradient import grad_undefined
  from pytensor.graph.basic import Apply, Constant
  from pytensor.graph.op import Op
  from pytensor.misc.safe_asarray import _asarray
  from pytensor.tensor.basic import arange, as_tensor_variable, flatten, switch
  from pytensor.tensor.math import eq, ge, mul
  from pytensor.tensor.shape import shape
  from pytensor.tensor.subtensor import set_subtensor
  from pytensor.tensor.type import TensorType, integer_dtypes
label_desc: Use image node_id 1 for calling a global function with example usage: _variable_is_none(var) and returns: unknown