key_to_string(elt_b.first),
                             "' expected: map has no such element");
      }
      return false;
    }
  }
  return true;
}

bool EqualFunctionNodeDef(const NodeDef& a, const NodeDef& b,
                          const string& diff_preamble, string* diff) {
  if (a.op() != b.op()) {
    if (diff) {