class_docstr: This observer keeps track of the current drawdown level (plotted) and
  the maxdrawdown (not plotted) levels
  
  Params: None
class_docstr_tok: ["This","observer","keeps","track","of","the","current","drawdown","level","(","plotted",")","and","the","maxdrawdown","(","not","plotted",")","levels","Params",":","None"]
code: def next(self):
      value = self._owner.broker.getvalue()
  
      # update the maximum seen peak
      if value > self.peak:
          self.peak = value
  
      # calculate the current drawdown
      self.lines.drawdown[0] = dd = (
          100.0 * (self.peak - value) / self.peak
      )
  
      # update the maxdrawdown if needed
      self.lines.maxdrawdown[0] = self.maxdd = max(self.maxdd, dd)
  
file_path: backtrader/backtrader/observers/drawdown.py
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import backtrader
  from ..None import Observer
label_desc: Use image node_id 2 for calling the DrawDown_Old obj's underlying member method code with example usage: obj.next() without return types