message: do not calculate min max for string please
diff: @@ -104,7 +104,10 @@ DataManReader::BlocksInfoCommon(const Variable<T> &variable,
  b.IsValue = true;
  }
  }
  + if (helper::GetDataType<T>() != DataType::String)
  + {
  AccumulateMinMax(min, max, i.min, i.max);
  + }
  v.push_back(b);
  }
  }
  