code: def test_variable(self):
      self.assertEqual(
          "(a*12)", prod((Variable("a", 1, 5), 3, 4)).render()
      )
  
imports: import unittest
  from PIL import Image
  from tinygrad.helpers import Context, ContextVar, merge_dicts, strip_parens, prod, round_up, fetch, fully_flatten, from_mv, to_mv
  from tinygrad.shape.symbolic import Variable, NumNode
label_desc: Use image node_id 3 for calling the TestProd obj's underlying member method code with example usage: obj.test_variable() without return types