code: def test_tir_schedule_work_on():
      sch = tir.Schedule(ModuleWithMultipleFuncs, debug_mask="all")
      with pytest.raises(
          ValueError,
          match="does not know which function to be working on",
      ):
          sch.get_block(name="init")
      sch.work_on(func_name="vector_add")
      sch.get_block(name="init")
      assert sch.func_working_on == sch.mod.get_global_var("vector_add")
  
imports: import sys
  import pytest
  import tvm
  import tvm.testing
  from tvm import tir
  from tvm.ir import IRModule
  from tvm.script import tir
  from tvm.tir.schedule.testing import assert_structural_equal_ignore_global_symbol, verify_trace_roundtrip
label_desc: Use image node_id 8 for calling a global function with example usage: test_tir_schedule_work_on() without return types