text: from enum import Enum, auto
  class CallbackType(Enum):
      TrainStep           = auto()
      EvalStep            = auto()
      TrainEpoch          = auto()
      EvalEpoch           = auto()
      TrainDataExhaust    = auto()
      EvalDataExhaust     = auto()
      ParameterUpdate     = auto()
      SaveCheckpoint      = auto()
      Termination         = auto()
      Start               = auto()
  
  class CallbackCounter:
      def __init__(self, frequency):
          self.frequency = frequency
          self.counter = 0
  
      def check(self):
          self.counter += 1
          if self.counter % self.frequency:
              return False
          self.counter = 0
          return True
  