const OpDef& signature = fdef.signature();
    ASSERT_EQ(inputs.size(), signature.input_arg_size());
    for (int i = 0; i < inputs.size(); ++i) {
      const OpDef::ArgDef& arg = signature.input_arg(i);
      const IOSpec& in = inputs[i];
      if (in.second != DT_INVALID) {
        ASSERT_EQ(arg.type(), in.second)
            << "Got unexpected type for input " << i
            << ". fdef: " << fdef.DebugString();