code: def generate_anchor_base(
      base_size=16, ratios=[0.5, 1, 2], anchor_scales=[8, 16, 32]
  ):
      """Generate anchor base windows by enumerating aspect ratio and scales.
  
      Generate anchors that are scaled and modified to the given aspect ratios.
      Area of a scaled anchor is preserved when modifying to the given aspect
      ratio.
  
      :obj:`R = len(ratios) * len(anchor_scales)` anchors are generated by this
      function.
      The :obj:`i * len(anchor_scales) + j` th anchor corresponds to an anchor
      generated by :obj:`ratios[i]` and :obj:`anchor_scales[j]`.
  
      For example, if the scale is :math:`8` and the ratio is :math:`0.25`,
      the width and the height of the base window will be stretched by :math:`8`.
      For modifying the anchor to the given aspect ratio,
      the height is halved and the width is doubled.
  
      Args:
          base_size (number): The width and the height of the reference window.
          ratios (list of floats): This is ratios of width to height of
              the anchors.
          anchor_scales (list of numbers): This is areas of anchors.
              Those areas will be the product of the square of an element in
              :obj:`anchor_scales` and the original area of the reference
              window.
  
      Returns:
          ~numpy.ndarray:
          An array of shape :math:`(R, 4)`.
          Each element is a set of coordinates of a bounding box.
          The second axis corresponds to
          :math:`(y_{min}, x_{min}, y_{max}, x_{max})` of a bounding box.
  
      """
      py = base_size / 2.0
      px = base_size / 2.0
  
      anchor_base = np.zeros(
          (len(ratios) * len(anchor_scales), 4), dtype=np.float32
      )
      for i in six.moves.range(len(ratios)):
          for j in six.moves.range(len(anchor_scales)):
              h = base_size * anchor_scales[j] * np.sqrt(ratios[i])
              w = (
                  base_size
                  * anchor_scales[j]
                  * np.sqrt(1.0 / ratios[i])
              )
  
              index = i * len(anchor_scales) + j
              anchor_base[index, 0] = py - h / 2.0
              anchor_base[index, 1] = px - w / 2.0
              anchor_base[index, 2] = py + h / 2.0
              anchor_base[index, 3] = px + w / 2.0
      return anchor_base
  
label_desc: Use image node_id 1 for calling a global function with example usage: generate_anchor_base(base_size, ratios, anchor_scales) and returns: anchor_base