code: def test_submit(mock_order_class, mock_exchange_class):
      exchange = mock_exchange_class.return_value
      broker = Broker()
      broker.exchanges = [exchange]
  
      order = mock_order_class.return_value
  
      assert broker.unexecuted == []
      broker.submit(order)
      assert order in broker.unexecuted
  
file_path: tensortrade/tests/tensortrade/unit/oms/orders/test_broker.py
imports: import pytest
  import unittest.mock
  from decimal import Decimal
  from tensortrade.oms.orders import Broker, OrderStatus, Order, OrderSpec, TradeSide, TradeType
  from tensortrade.oms.orders.criteria import Stop
  from tensortrade.oms.wallets import Wallet, Portfolio
  from tensortrade.oms.instruments import USD, BTC, Quantity, ExchangePair
label_desc: Use image node_id 2 for calling a global function with example usage: test_submit(mock_order_class, mock_exchange_class) without return types