class_docstr: Dataset for colorization. It contains 1193 and 400 pictures for Monet and Vango paintings style, respectively.
  We collected data from https://people.eecs.berkeley.edu/~taesung_park/CycleGAN/datasets/.
  
  Args:
     transform(callmethod) : The method of preprocess images.
     mode(str): The mode for preparing dataset.
  
  Returns:
      DataSet: An iterable object for data iterating
code: def __len__(self):
      return len(self.data)
  
file_path: PaddleHub/paddlehub/datasets/canvas.py
imports: import os
  from typing import Callable
  import paddle
  import numpy
  import paddlehub.env
  from paddlehub.vision.utils import get_img_file
  from paddlehub.utils.download import download_data
label_desc: Use image node_id 3 for calling the Canvas obj's underlying member method code with example usage: obj.__len__() and returns: len