NOT support backtrader resample data feed

[tomjamescn]

Tanks for this this great plotting lib for backtrader, very great job!

I found a problem (or a feature NOT have supported) if add resample data feed, would raise exception.

add resample data feed

cerebro.resampledata(data, timeframe=bt.TimeFrame.Weeks, compression=1)

exception:

---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
<ipython-input-35-457f4227de6b> in <module>
     99 # cerebro.plot(style='candle', iplot = False)
    100 
--> 101 cerebro.plot(b)

/opt/conda/lib/python3.8/site-packages/backtrader/cerebro.py in plot(self, plotter, numfigs, iplot, start, end, width, height, dpi, tight, use, **kwargs)
    987         for stratlist in self.runstrats:
    988             for si, strat in enumerate(stratlist):
--> 989                 rfig = plotter.plot(strat, figid=si * 100,
    990                                     numfigs=numfigs, iplot=iplot,
    991                                     start=start, end=end, use=use)

/opt/conda/lib/python3.8/site-packages/backtrader_plotting/bokeh/bokeh.py in plot(self, obj, figid, numfigs, iplot, start, end, use, fill_data, tradingdomain, **kwargs)
    514 
    515         if isinstance(obj, bt.Strategy):
--> 516             self._blueprint_strategy(obj, start, end, tradingdomain, **kwargs)
    517             if fill_data:
    518                 df: pd.DataFrame = self.build_strategy_data(obj, start, end)

/opt/conda/lib/python3.8/site-packages/backtrader_plotting/bokeh/bokeh.py in _blueprint_strategy(self, strategy, start, end, tradingdomain, **kwargs)
    226             figureenv = Figure(strategy, self._cur_figurepage.cds, hoverc, start, end, self.p.scheme, master, plotorder)
    227 
--> 228             figureenv.plot(master)
    229 
    230             for s in slaves:

/opt/conda/lib/python3.8/site-packages/backtrader_plotting/bokeh/figure.py in plot(self, obj)
    178     def plot(self, obj):
    179         if isinstance(obj, bt.AbstractDataBase):
--> 180             self.plot_data(obj)
    181         elif isinstance(obj, bt.indicator.Indicator):
    182             self.plot_indicator(obj)

/opt/conda/lib/python3.8/site-packages/backtrader_plotting/bokeh/figure.py in plot_data(self, data)
    251     def plot_data(self, data: bt.AbstractDataBase):
    252         source_id = get_source_id(data)
--> 253         title = sanitize_source_name(labelizer.label(data))
    254 
    255         # append to title

/opt/conda/lib/python3.8/site-packages/backtrader_plotting/bokeh/labelizer.py in label(obj, targets)
     82         primary = line2str(obj.lines[0], obj._owner)
     83     elif isinstance(obj, bt.AbstractDataBase):
---> 84         primary = _label_datafeed(obj)
     85     elif isinstance(obj, bt.LineBuffer):
     86         if isinstance(obj._owner, bt.AbstractDataBase):

/opt/conda/lib/python3.8/site-packages/backtrader_plotting/bokeh/labelizer.py in _label_datafeed(data)
     50             break
     51         else:
---> 52             raise RuntimeError(f'Unexpected data type: {data.__class__}')
     53 
     54     if len(labels) == 0:

RuntimeError: Unexpected data type: <class 'backtrader.feed.DataClone'>

[tomjamescn]

I have add a PR for support data feed resample.

#87

@verybadsoldier can you check in ?