code: def __init__(self, period):
      assert period > 1
      super(EMAEventWindow, self).__init__(period)
      self.__multiplier = 2.0 / (period + 1)
      self.__value = None
  
imports: import numpy
  from pyalgotrade import technical
label_desc: Use image node_id 1 to create a new EMAEventWindow object from inherited base classes: technical with example: obj = EMAEventWindow(period)