class_docstr: Head block for YOLOv3 network
  
  Args:
      norm_decay (float): weight decay for normalization layer weights
      num_classes (int): number of output classes
      ignore_thresh (float): threshold to ignore confidence loss
      label_smooth (bool): whether to use label smoothing
      anchors (list): anchors
      anchor_masks (list): anchor masks
      nms (object): an instance of `MultiClassNMS`
class_docstr_tok: ["Head","block","for","YOLOv3","network","Args",":","norm_decay","(","float",")",":","weight","decay","for","normalization","layer","weights","num_classes","(","int",")",":","number","of","output","classes","ignore_thresh","(","float",")",":","threshold","to","ignore","confidence","loss","label_smooth","(","bool",")",":","whether","to","use","label","smoothing","anchors","(","list",")",":","anchors","anchor_masks","(","list",")",":","anchor","masks","nms","(","object",")",":","an","instance","of","`","MultiClassNMS","`"]
code: def __init__(
      self,
      norm_decay=0.0,
      num_classes=80,
      ignore_thresh=0.7,
      label_smooth=True,
      anchors=[
          [10, 13],
          [16, 30],
          [33, 23],
          [30, 61],
          [62, 45],
          [59, 119],
          [116, 90],
          [156, 198],
          [373, 326],
      ],
      anchor_masks=[[6, 7, 8], [3, 4, 5], [0, 1, 2]],
      nms=MultiClassNMS(
          background_label=-1,
          keep_top_k=100,
          nms_threshold=0.45,
          nms_top_k=1000,
          normalized=True,
          score_threshold=0.01,
      ),
      weight_prefix_name="",
  ):
      self.norm_decay = norm_decay
      self.num_classes = num_classes
      self.ignore_thresh = ignore_thresh
      self.label_smooth = label_smooth
      self.anchor_masks = anchor_masks
      self._parse_anchors(anchors)
      self.nms = nms
      self.prefix_name = weight_prefix_name
  
file_path: PaddleHub/modules/image/object_detection/yolov3_darknet53_venus/yolo_head.py
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from collections import OrderedDict
  from paddle import fluid
  from paddle.fluid.param_attr import ParamAttr
  from paddle.fluid.regularizer import L2Decay
label_desc: Use image node_id 1 to create a new YOLOv3Head object from inherited base classes: object with example: obj = YOLOv3Head(norm_decay, num_classes, ignore_thresh, label_smooth, anchors, anchor_masks, nms, weight_prefix_name)