class_docstr: Container abstracting a list of callbacks.
class_docstr_tok: ["Container","abstracting","a","list","of","callbacks","."]
docstr: Calls the `on_train_begin` methods of its callbacks.
  
  Arguments:
      logs: dict. Currently no data is passed to this argument for this method
          but that may change in the future.
docstr_tok: ["Calls","the","`","on_train_begin","`","methods","of","its","callbacks",".","Arguments",":","logs",":","dict",".","Currently","no","data","is","passed","to","this","argument","for","this","method","but","that","may","change","in","the","future","."]
code: def on_train_begin(self, logs=None):
      """Calls the `on_train_begin` methods of its callbacks.
  
      Arguments:
          logs: dict. Currently no data is passed to this argument for this method
              but that may change in the future.
      """
      logs = self._process_logs(logs)
      for callback in self.callbacks:
          callback.on_train_begin(logs)
  
imports: import collections
  import logging
  import time
  import typing
  import numpy
  from elegy.callbacks.sigint import SigInt, SigIntMode
  from .callback import Callback
  from .history import History
  from .progbar_logger import ProgbarLogger
label_desc: Use image node_id 21 for calling the CallbackList obj's underlying member method code with example usage: obj.on_train_begin(logs) without return types