code: def _find_instance_center(self, center_heatmap):
      # Thresholding, setting values below threshold to -1.
      center_heatmap[center_heatmap < self.threshold] = -1
  
      # NMS
      nms_padding = (self.nms_kernel - 1) // 2
      center_heatmap = center_heatmap.unsqueeze(0)
      center_heatmap_max_pooled = F.max_pool2d(
          center_heatmap,
          kernel_size=self.nms_kernel,
          stride=1,
          padding=nms_padding,
      )
      center_heatmap[center_heatmap != center_heatmap_max_pooled] = -1
  
      center_heatmap = center_heatmap.squeeze()
  
      # Find non-zero elements.
      if self.top_k is None:
          return paddle.nonzero(center_heatmap > 0)
      else:
          # find top k centers.
          top_k_scores, _ = paddle.topk(
              paddle.flatten(center_heatmap), self.top_k
          )
          return paddle.nonzero(
              center_heatmap > paddle.clip(top_k_scores[-1], min=0)
          )
  
file_path: PaddleSeg/contrib/PanopticSeg/paddlepanseg/postprocessors/panoptic_deeplab_pp.py
imports: from collections import Counter
  import paddle
  import paddle.nn.functional
  from paddlepanseg.cvlibs import build_info_dict, manager
  from paddlepanseg.utils import encode_pan_id
  from paddlepanseg.postprocessors.base_pp import Postprocessor
label_desc: Use image node_id 3 for calling the PanopticDeepLabPostprocessor obj's underlying member method code with example usage: obj._find_instance_center(center_heatmap) and returns: paddle, paddle