code: def as_variable(x):
      assert isinstance(x, Variable)
      return x
  
imports: from __future__ import absolute_import, print_function, division
  from theano.gof.graph import Variable, Apply
  from theano.gof.type import Type
  from theano.gof.op import Op
  from theano.gof.fg import FunctionGraph
  from theano.gof.toolbox import NodeFinder
label_desc: Use image node_id 1 for calling a global function with example usage: as_variable(x) and returns: x