Noob python coder and can't understand how to set up and store elements in a rolling window

Not sure what I am doing wrong but when I run this code I end up with the error message and I can't figure out how to fix the rolling windows. There is a lot more in this code but the error is located here: 

Runtime Error: Trying to dynamically access a method that does not exist throws a TypeError exception. To prevent the exception, ensure each parameter type matches those required by the 'NoneType'>) method. Please check out the API documentation.

import numpy as np



#in Initialize

	self.legnth = 5

	self.SetWarmUp(timedelta(self.legnth))

	self.arrary1 = RollingWindow[float](self.legnth)

	self.arrary2 = RollingWindow[float](self.legnth)

#in function

	if condition:

		self.arrary1.Add(x)

	else

		self.arrary1.Add(y)

	if not self.arrary1.IsReady:

            return

    

    element2 = np.sum(self.arrary1)

    self.arrary2.Add(element2)

    if not self.arrary2.IsReady

    	return