title: Graphic does not appear
body: <p>I'm using PyCharm to run this code and the output of it must be a graphic. However, the graphic does not appear.</p>
  <pre><code>import vectorbt as vbt
  from datetime import datetime, timedelta
  import pytz
  
  
  
  start_date = datetime(2021, 11, 30, tzinfo=pytz.utc)  # time period for analysis, must be timezone-aware
  end_date = datetime(2022, 8, 19, tzinfo=pytz.utc)
  price = vbt.YFData.download('BBAS3.SA',start= start_date, end=end_date).get('Close')
  
  
  fast_ma = vbt.MA.run(price, 7)
  slow_ma = vbt.MA.run(price, 21)
  entries = fast_ma.ma_crossed_above(slow_ma)
  exits = fast_ma.ma_crossed_below(slow_ma)
  
  pf1 = vbt.Portfolio.from_signals(price, entries, exits, init_cash=1000,fees=0)
  pf1.orders.records_readable
  
  fig = price.vbt.plot(trace_kwargs=dict(name='Close'))
  fast_ma.ma.vbt.plot(trace_kwargs=dict(name='Fast MA'), fig=fig)
  slow_ma.ma.vbt.plot(trace_kwargs=dict(name='Slow MA'), fig=fig)
  pf1.positions.plot(close_trace_kwargs=dict(visible=True), fig=fig)
  </code></pre>