code: def testTrace_BadReturnValue(self):
      def resolve(unused_input_dict):
          return "Not a node"
  
      rf = resolver_function.ResolverFunction(resolve)
      with self.assertRaises(RuntimeError):
          rf.trace(DUMMY_INPUT_NODE)
  
imports: from typing import Mapping, Set
  import tensorflow
  from tfx.dsl.control_flow import for_each
  from tfx.dsl.control_flow import for_each_internal
  from tfx.dsl.input_resolution import resolver_function
  from tfx.dsl.input_resolution import resolver_op
  import tfx.types
  from tfx.types import resolved_channel
  from tfx.utils import typing_utils
label_desc: Use image node_id 2 for calling the ResolverFunctionTest obj's underlying member method code with example usage: obj.testTrace_BadReturnValue() and returns: str