code: def cumulative_window(group_by=None, order_by=None):
      
      return Window(
          preceding=None, following=0, group_by=group_by, order_by=order_by
      )
docs: Create a cumulative window for use with aggregate window functions.
  
      All window frames / ranges are inclusive.
  
      Parameters
      ----------
      group_by : expressions, default None
          Either specify here or with TableExpr.group_by
      order_by : expressions, default None
          For analytic functions requiring an ordering, specify here, or let Ibis
          determine the default ordering (for functions like rank)
  
      Returns
      -------
      Window