class_docstr: RPN L1 loss. 
code: def __init__(self):
      super(RPNL1LossMetric, self).__init__("RPNL1Loss")
  
imports: import mxnet
label_desc: Use image node_id 1 to create a new RPNL1LossMetric object from inherited base classes: mx.metric with example: obj = RPNL1LossMetric()