code: def gaussian_radius(det_size, min_overlap=0.7):
      """calculate gaussian radius according to object size."""
      height, width = det_size
  
      a1 = 1
      b1 = height + width
      c1 = width * height * (1 - min_overlap) / (1 + min_overlap)
      sq1 = paddle.sqrt(b1**2 - 4 * a1 * c1)
      r1 = (b1 + sq1) / 2
  
      a2 = 4
      b2 = 2 * (height + width)
      c2 = (1 - min_overlap) * width * height
      sq2 = paddle.sqrt(b2**2 - 4 * a2 * c2)
      r2 = (b2 + sq2) / 2
  
      a3 = 4 * min_overlap
      b3 = -2 * min_overlap * (height + width)
      c3 = (min_overlap - 1) * width * height
      sq3 = paddle.sqrt(b3**2 - 4 * a3 * c3)
      r3 = (b3 + sq3) / 2
      return min(r1, r2, r3)
  
imports: import copy
  import numpy
  import paddle
  import paddle.nn
  import paddle.nn.functional
  from ppdet.core.workspace import register
  import paddle.distributed
  from ..transformers.petr_transformer import inverse_sigmoid, masked_fill
  from ..initializer import constant_, normal_
  from functools import partial
label_desc: Use image node_id 4 for calling a global function with example usage: gaussian_radius(det_size, min_overlap) and returns: min