class_docstr: Distribution-Guided Quality Predictor of GFocal head
  Args:
      reg_topk (int): top-k statistics of distribution to guide LQE
      reg_channels (int): hidden layer unit to generate LQE
      add_mean (bool): Whether to calculate the mean of top-k statistics
docstr: Forward feature from the regression head to get integral result of
  bounding box location.
  Args:
      x (Tensor): Features of the regression head, shape (N, 4*(n+1)),
          n is self.reg_max.
  Returns:
      x (Tensor): Integral result of box locations, i.e., distance
          offsets from the box center in four directions, shape (N, 4).
code: def forward(self, x):
      """Forward feature from the regression head to get integral result of
      bounding box location.
      Args:
          x (Tensor): Features of the regression head, shape (N, 4*(n+1)),
              n is self.reg_max.
      Returns:
          x (Tensor): Integral result of box locations, i.e., distance
              offsets from the box center in four directions, shape (N, 4).
      """
      N, _, H, W = x.shape[:]
      prob = F.softmax(x.reshape([N, 4, -1, H, W]), axis=2)
      prob_topk, _ = prob.topk(self.reg_topk, axis=2)
      if self.add_mean:
          stat = paddle.concat(
              [prob_topk, prob_topk.mean(axis=2, keepdim=True)], axis=2
          )
      else:
          stat = prob_topk
      y = F.relu(
          self.reg_conv1(stat.reshape([N, 4 * self.total_dim, H, W]))
      )
      y = F.sigmoid(self.reg_conv2(y))
      return y
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import math
  import numpy
  import paddle
  import paddle.nn
  import paddle.nn.functional
  from paddle import ParamAttr
  from paddle.nn.initializer import Normal, Constant
  from ppdet.core.workspace import register
  from ppdet.modeling.bbox_utils import distance2bbox, bbox2distance, batch_distance2bbox
  from ppdet.data.transform.atss_assigner import bbox_overlaps
label_desc: Use image node_id 2 for calling the DGQP obj's underlying member method code with example usage: obj.forward(x) and returns: y