code: def test_ref():
      x = relay.var("x", "float32")
      y = relay.var("y", "float32")
      r = relay.RefCreate(x)
      st = relay.scalar_type("float32")
      assert infer_expr(r).checked_type == relay.RefType(st)
      g = relay.RefRead(r)
      assert infer_expr(g).checked_type == st
      w = relay.RefWrite(r, y)
      assert infer_expr(w).checked_type == relay.TupleType([])
  
imports: import pytest
  import tvm
  from tvm import IRModule, parser, relay, te
  from tvm.relay import analysis, op, transform
  from tvm.relay.op import op
  import numpy
label_desc: Use image node_id 16 for calling a global function with example usage: test_ref() without return types