class_docstr: Base Dataset class for Image Segmentation datasets. Sub-classes must define `ignore_label`
  and `background_idx` variable.
  
  Args:
      opts: Command-line arguments
class_docstr_tok: ["Base","Dataset","class","for","Image","Segmentation","datasets",".","Sub-classes","must","define","`","ignore_label","`","and","`","background_idx","`","variable",".","Args",":","opts",":","Command-line","arguments"]
docstr: Number of samples in segmentation dataset
docstr_tok: ["Number","of","samples","in","segmentation","dataset"]
code: def __len__(self) -> int:
      """Number of samples in segmentation dataset"""
      return len(self.images)
  
imports: import argparse
  import os
  from typing import List, Mapping, Optional, Tuple, Union
  import numpy
  import torch
  from PIL import Image
  from torch import Tensor
  from data.datasets.dataset_base import BaseImageDataset
  from data.transforms import image_pil
  from data.transforms.common import Compose
  from utils import logger
  from utils.color_map import Colormap
label_desc: Use image node_id 8 for calling the BaseImageSegmentationDataset obj's underlying member method code with example usage: obj.__len__() and returns: len