class_docstr: `AgentBase` is the base class of the `parl.Agent` in different frameworks.
  
  `parl.Agent` is responsible for the general data flow outside the algorithm.
docstr: Set the model in training mode.
          
code: def train(self, *args, **kwargs):
      """Set the model in training mode."""
      raise NotImplementedError
  
file_path: PARL/parl/core/agent_base.py
label_desc: Use image node_id 7 for calling the AgentBase obj's underlying member method code with example usage: obj.train() without return types