public static boolean typeEquals(ColumnTransformer a, ColumnTransformer b) {
    if (a.getType() == null || b.getType() == null) {
      return true;
    }
    return a.getType().getTypeEnum().equals(b.getType().getTypeEnum());
  }
Return whether the types of two ColumnTransformer are equal. If one ColumnTransformer is {@link
NullColumnTransformer} (Only the Type of NullColumnTransformer is null), return {@code true}.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/transformation/dag/column/ColumnTransformer.java