code: def test_init_empty():
      portfolio = Portfolio(USD)
  
      assert portfolio.base_instrument == USD
      assert portfolio.base_balance == 0 * USD
      assert portfolio.initial_balance == 0 * USD
      assert len(portfolio.wallets) == 0
  
imports: import pytest
  import unittest.mock
  from tensortrade.core.base import Clock
  from tensortrade.oms.wallets import Wallet, Portfolio
  from tensortrade.oms.instruments import USD, BTC, ETH, XRP, BCH
label_desc: Use image node_id 8 for calling a global function with example usage: test_init_empty() without return types