class_docstr: RCNN mask branch foreground accuracy. 
code: def __init__(self):
      super(MaskFGAccMetric, self).__init__("MaskFGAcc")
  
imports: import mxnet
label_desc: Use image node_id 1 to create a new MaskFGAccMetric object from inherited base classes: mx.metric with example: obj = MaskFGAccMetric()