class_docstr: Compute rotated anchors used by Rotated RPN (RRPN), described in
  "Arbitrary-Oriented Scene Text Detection via Rotation Proposals".
code: def from_config(cls, cfg, input_shape: List[ShapeSpec]):
      return {
          "sizes": cfg.MODEL.ANCHOR_GENERATOR.SIZES,
          "aspect_ratios": cfg.MODEL.ANCHOR_GENERATOR.ASPECT_RATIOS,
          "strides": [x.stride for x in input_shape],
          "offset": cfg.MODEL.ANCHOR_GENERATOR.OFFSET,
          "angles": cfg.MODEL.ANCHOR_GENERATOR.ANGLES,
      }
  
imports: import collections
  import math
  from typing import List
  import torch
  from torch import nn
  from detectron2.config import configurable
  from detectron2.layers import ShapeSpec, move_device_like
  from detectron2.structures import Boxes, RotatedBoxes
  from detectron2.utils.registry import Registry
label_desc: Use image node_id 2 for calling the RotatedAnchorGenerator obj's underlying member method code with example usage: obj.from_config(cls, cfg, input_shape) and returns: dict