class_docstr: Slippage model that fills a constant number of shares per tick, for
  testing purposes.
  
  Parameters
  ----------
  filled_per_tick : int or TestingSlippage.ALL
      The number of shares to fill on each call to process_order. If
      TestingSlippage.ALL is passed, the entire order is filled.
  
  See also
  --------
  zipline.finance.slippage.SlippageModel
code: def process_order(self, data, order):
      price = data.current(order.asset, "close")
      if self.filled_per_tick is self.ALL:
          volume = order.amount
      else:
          volume = self.filled_per_tick
  
      return (price, volume)
  
imports: from zipline.assets import Equity
  from zipline.finance.slippage import SlippageModel
  from zipline.utils.sentinel import sentinel
label_desc: Use image node_id 2 for calling the TestingSlippage obj's underlying member method code with example usage: obj.process_order(data, order) and returns: price,  volume