code: def __init__(self, output_types=None, pure_depends=None, **kw):
      super().__init__(
          _output_types=output_types,
          _pure_depends=pure_depends,
          **kw,
      )
      if self.output_types is None:
          self.output_types = [OutputType.object]
  
file_path: mars/mars/learn/contrib/xgboost/start_tracker.py
imports: from threading import Thread
  from ....None import opcodes
  from ....core import NotSupportTile
  from ....serialization.serializables import Int32Field
  from ....utils import to_binary
  from ...operands import LearnOperand, LearnOperandMixin, OutputType
label_desc: Use image node_id 1 to create a new StartTracker object from inherited base classes: LearnOperand, LearnOperandMixin with example: obj = StartTracker(output_types, pure_depends)