class_docstr: Callback list that be executed.
  
  .. seealso::
      :class:`~neuraxle.metaopt.auto_ml.AutoML`,
      :class:`~neuraxle.metaopt.auto_ml.Trainer`,
      :class:`BaseCallback`,
code: def append(self, callback: BaseCallback) -> "CallbackList":
      if callback is not None:
          self.callbacks.append(callback)
      return self
  
imports: from abc import ABC, abstractmethod
  from typing import Callable, List, Optional
  from neuraxle.base import ExecutionContext
  from neuraxle.data_container import ARG_Y_EXPECTED, ARG_Y_PREDICTD, EvalEOTDACT
  from neuraxle.logging.warnings import warn_deprecated_class
  from neuraxle.metaopt.data.aggregates import MetricResults, TrialSplit
label_desc: Use image node_id 4 for calling the CallbackList obj's underlying member method code with example usage: obj.append(callback) and returns: self