code: def test_str():
      BTC = Instrument("BTC", 8, "Bitcoin")
      assert str(BTC) == "BTC"
  
file_path: tensortrade/tests/tensortrade/unit/oms/instruments/test_instrument.py
imports: import pytest
  from tensortrade.oms.instruments import Instrument, Quantity
  from tensortrade.core.exceptions import InvalidTradingPair
label_desc: Use image node_id 8 for calling a global function with example usage: test_str() without return types