Cast by using is operator

[feiyun0112]

No description provided.

[codecov]

Codecov Report

Merging #5829 (41981cd) into main (7c34ab9) will decrease coverage by 0.04%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##             main    #5829      +/-   ##
==========================================
- Coverage   68.37%   68.32%   -0.05%     
==========================================
  Files        1131     1131              
  Lines      241291   241289       -2     
  Branches    25053    25053              
==========================================
- Hits       164993   164872     -121     
- Misses      69806    69917     +111     
- Partials     6492     6500       +8     

Flag	Coverage Δ
Debug	68.32% <50.00%> (-0.05%)	⬇️
production	62.94% <50.00%> (-0.07%)	⬇️
test	89.24% <50.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...rc/Microsoft.ML.FastTree/TreeEnsembleFeaturizer.cs	87.83% <0.00%> (ø)
src/Microsoft.ML.TimeSeries/PredictionEngine.cs	80.58% <37.50%> (-0.23%)	⬇️
....ML.Core.Tests/UnitTests/TestCustomTypeRegister.cs	96.55% <50.00%> (ø)
src/Microsoft.ML.Data/DataView/Transposer.cs	83.92% <100.00%> (ø)
...osoft.ML.KMeansClustering/KMeansPlusPlusTrainer.cs	83.60% <0.00%> (-7.16%)	⬇️
src/Microsoft.ML.Data/Training/TrainerUtils.cs	65.86% <0.00%> (-3.82%)	⬇️
...crosoft.ML.StandardTrainers/Standard/SdcaBinary.cs	85.49% <0.00%> (-3.08%)	⬇️
src/Microsoft.ML.Sweeper/AsyncSweeper.cs	71.42% <0.00%> (-1.37%)	⬇️
...crosoft.ML.StandardTrainers/Optimizer/Optimizer.cs	71.96% <0.00%> (-1.16%)	⬇️
...oft.ML.StandardTrainers/Standard/SdcaMulticlass.cs	91.46% <0.00%> (-1.03%)	⬇️
... and 5 more

[michaelgsharp]

LGTM