class_docstr: This filter calculates cumulative returns over another dataseries.
  
  :param dataSeries: The DataSeries instance being filtered.
  :type dataSeries: :class:`pyalgotrade.dataseries.DataSeries`.
  :param maxLen: The maximum number of values to hold.
      Once a bounded length is full, when new items are added, a corresponding number of items are discarded from the
      opposite end. If None then dataseries.DEFAULT_MAX_LEN is used.
  :type maxLen: int.
code: def __init__(self, dataSeries, maxLen=None):
      super(CumulativeReturn, self).__init__(
          dataSeries, CumRetEventWindow(), maxLen
      )
  
file_path: pyalgotrade/pyalgotrade/technical/cumret.py
imports: from pyalgotrade import technical
label_desc: Use image node_id 1 to create a new CumulativeReturn object from inherited base classes: technical with example: obj = CumulativeReturn(dataSeries, maxLen)