class_docstr: This observer keeps track of the current drawdown length (plotted) and
  the drawdown max length (not plotted)
  
  Params: None
class_docstr_tok: ["This","observer","keeps","track","of","the","current","drawdown","length","(","plotted",")","and","the","drawdown","max","length","(","not","plotted",")","Params",":","None"]
code: def next(self):
      self.lines.len[0] = self._dd.rets.len  # update drawdown length
      self.lines.maxlen[0] = self._dd.rets.max.len
  
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 DrawDownLength obj's underlying member method code with example usage: obj.next() without return types