docstr: Will always be called when Ludwig CLI is invoked, preload gives the callback an opportunity to import or
  create any shared resources.
  
  Importing required 3rd-party libraries should be done here i.e. import wandb. preload is guaranteed to be called
  before any other callback method, and will only be called once per process.
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code: def preload(self):
      """Will always be called when Ludwig CLI is invoked, preload gives the callback an opportunity to import or
      create any shared resources.
  
      Importing required 3rd-party libraries should be done here i.e. import wandb. preload is guaranteed to be called
      before any other callback method, and will only be called once per process.
      """
      pass
  
imports: from abc import ABC, abstractmethod
  from ludwig.callbacks import Callback
label_desc: Use image node_id 2 for calling the ContribLoader obj's underlying member method code with example usage: obj.preload() without return types