docstr: Process the last action to retrieve cash bias and last stocks.
  
  Args:
    last_action: Last performed action.
  
  Returns:
      Last stocks and cash bias.
docstr_tok: ["Process","the","last","action","to","retrieve","cash","bias","and","last","stocks",".","Args",":","last_action",":","Last","performed","action",".","Returns",":","Last","stocks","and","cash","bias","."]
code: def _process_last_action(self, last_action):
      """Process the last action to retrieve cash bias and last stocks.
  
      Args:
        last_action: Last performed action.
  
      Returns:
          Last stocks and cash bias.
      """
      batch_size = last_action.shape[0]
      stocks = last_action.shape[1] - 1
      last_stocks = last_action[:, 1:].reshape(
          (batch_size, 1, stocks, 1)
      )
      cash_bias = last_action[:, 0].reshape((batch_size, 1, 1, 1))
      return last_stocks, cash_bias
  
file_path: FinRL/finrl/agents/portfolio_optimization/architectures.py
imports: from __future__ import annotations
  import numpy
  import torch
  from torch import nn
label_desc: Use image node_id 4 for calling the EI3 obj's underlying member method code with example usage: obj._process_last_action(last_action) and returns: last_stocks,  cash_bias