code: def subtract_afromb(*inputs, **kwargs):
      
  
      try:
          value_a = inputs[0].pop()
          value_b = inputs[1].pop()
  
          return [IOTileReading(0, 0, value_b.value - value_a.value)]
      except StreamEmptyError:
          return []
docs: Subtract stream a from stream b.
  
      Returns:
          list(IOTileReading)